From: Steven Rostedt <rostedt@goodmis.org>
To: linux-kernel@vger.kernel.org
Cc: Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Tom Zanussi <tom.zanussi@linux.intel.com>,
Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
Namhyung Kim <namhyung@kernel.org>
Subject: [for-next][PATCH 22/30] tracing: Add hist trigger Documentation
Date: Wed, 20 Apr 2016 15:30:00 -0400 [thread overview]
Message-ID: <20160420193029.799008992@goodmis.org> (raw)
In-Reply-To: 20160420192938.515326341@goodmis.org
[-- Attachment #1: 0022-tracing-Add-hist-trigger-Documentation.patch --]
[-- Type: text/plain, Size: 68314 bytes --]
From: Tom Zanussi <tom.zanussi@linux.intel.com>
Add documentation and usage examples for 'hist' triggers.
Link: http://lkml.kernel.org/r/2e13f35f47fea6d647f0efefccfc9673ea84b29f.1457029949.git.tom.zanussi@linux.intel.com
Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com>
Tested-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Reviewed-by: Namhyung Kim <namhyung@kernel.org>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
Documentation/trace/events.txt | 1155 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 1155 insertions(+)
diff --git a/Documentation/trace/events.txt b/Documentation/trace/events.txt
index c010be8c85d7..db223e85bd2f 100644
--- a/Documentation/trace/events.txt
+++ b/Documentation/trace/events.txt
@@ -512,3 +512,1158 @@ The following commands are supported:
Note that there can be only one traceon or traceoff trigger per
triggering event.
+
+- hist
+
+ This command aggregates event hits into a hash table keyed on one or
+ more trace event format fields (or stacktrace) and a set of running
+ totals derived from one or more trace event format fields and/or
+ event counts (hitcount).
+
+ The format of a hist trigger is as follows:
+
+ hist:keys=<field1[,field2,...]>[:values=<field1[,field2,...]>]
+ [:sort=<field1[,field2,...]>][:size=#entries][:pause][:continue]
+ [:clear] [if <filter>]
+
+ When a matching event is hit, an entry is added to a hash table
+ using the key(s) and value(s) named. Keys and values correspond to
+ fields in the event's format description. Values must correspond to
+ numeric fields - on an event hit, the value(s) will be added to a
+ sum kept for that field. The special string 'hitcount' can be used
+ in place of an explicit value field - this is simply a count of
+ event hits. If 'values' isn't specified, an implicit 'hitcount'
+ value will be automatically created and used as the only value.
+ Keys can be any field, or the special string 'stacktrace', which
+ will use the event's kernel stacktrace as the key. The keywords
+ 'keys' or 'key' can be used to specify keys, and the keywords
+ 'values', 'vals', or 'val' can be used to specify values. Compound
+ keys consisting of up to two fields can be specified by the 'keys'
+ keyword. Hashing a compound key produces a unique entry in the
+ table for each unique combination of component keys, and can be
+ useful for providing more fine-grained summaries of event data.
+ Additionally, sort keys consisting of up to two fields can be
+ specified by the 'sort' keyword. If more than one field is
+ specified, the result will be a 'sort within a sort': the first key
+ is taken to be the primary sort key and the second the secondary
+ key.
+
+ 'hist' triggers add a 'hist' file to each event's subdirectory.
+ Reading the 'hist' file for the event will dump the hash table in
+ its entirety to stdout. Each printed hash table entry is a simple
+ list of the keys and values comprising the entry; keys are printed
+ first and are delineated by curly braces, and are followed by the
+ set of value fields for the entry. By default, numeric fields are
+ displayed as base-10 integers. This can be modified by appending
+ any of the following modifiers to the field name:
+
+ .hex display a number as a hex value
+ .sym display an address as a symbol
+ .sym-offset display an address as a symbol and offset
+ .syscall display a syscall id as a system call name
+ .execname display a common_pid as a program name
+
+ Note that in general the semantics of a given field aren't
+ interpreted when applying a modifier to it, but there are some
+ restrictions to be aware of in this regard:
+
+ - only the 'hex' modifier can be used for values (because values
+ are essentially sums, and the other modifiers don't make sense
+ in that context).
+ - the 'execname' modifier can only be used on a 'common_pid'. The
+ reason for this is that the execname is simply the 'comm' value
+ saved for the 'current' process when an event was triggered,
+ which is the same as the common_pid value saved by the event
+ tracing code. Trying to apply that comm value to other pid
+ values wouldn't be correct, and typically events that care save
+ pid-specific comm fields in the event itself.
+
+ A typical usage scenario would be the following to enable a hist
+ trigger, read its current contents, and then turn it off:
+
+ # echo 'hist:keys=skbaddr.hex:vals=len' > \
+ /sys/kernel/debug/tracing/events/net/netif_rx/trigger
+
+ # cat /sys/kernel/debug/tracing/events/net/netif_rx/hist
+
+ # echo '!hist:keys=skbaddr.hex:vals=len' > \
+ /sys/kernel/debug/tracing/events/net/netif_rx/trigger
+
+ The trigger file itself can be read to show the details of the
+ currently attached hist trigger. This information is also displayed
+ at the top of the 'hist' file when read.
+
+ By default, the size of the hash table is 2048 entries. The 'size'
+ parameter can be used to specify more or fewer than that. The units
+ are in terms of hashtable entries - if a run uses more entries than
+ specified, the results will show the number of 'drops', the number
+ of hits that were ignored. The size should be a power of 2 between
+ 128 and 131072 (any non- power-of-2 number specified will be rounded
+ up).
+
+ The 'sort' parameter can be used to specify a value field to sort
+ on. The default if unspecified is 'hitcount' and the default sort
+ order is 'ascending'. To sort in the opposite direction, append
+ .descending' to the sort key.
+
+ The 'pause' parameter can be used to pause an existing hist trigger
+ or to start a hist trigger but not log any events until told to do
+ so. 'continue' or 'cont' can be used to start or restart a paused
+ hist trigger.
+
+ The 'clear' parameter will clear the contents of a running hist
+ trigger and leave its current paused/active state.
+
+ Note that the 'pause', 'cont', and 'clear' parameters should be
+ applied using 'append' shell operator ('>>') if applied to an
+ existing trigger, rather than via the '>' operator, which will cause
+ the trigger to be removed through truncation.
+
+- enable_hist/disable_hist
+
+ The enable_hist and disable_hist triggers can be used to have one
+ event conditionally start and stop another event's already-attached
+ hist trigger. Any number of enable_hist and disable_hist triggers
+ can be attached to a given event, allowing that event to kick off
+ and stop aggregations on a host of other events.
+
+ The format is very similar to the enable/disable_event triggers:
+
+ enable_hist:<system>:<event>[:count]
+ disable_hist:<system>:<event>[:count]
+
+ Instead of enabling or disabling the tracing of the target event
+ into the trace buffer as the enable/disable_event triggers do, the
+ enable/disable_hist triggers enable or disable the aggregation of
+ the target event into a hash table.
+
+ A typical usage scenario for the enable_hist/disable_hist triggers
+ would be to first set up a paused hist trigger on some event,
+ followed by an enable_hist/disable_hist pair that turns the hist
+ aggregation on and off when conditions of interest are hit:
+
+ # echo 'hist:keys=skbaddr.hex:vals=len:pause' > \
+ /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
+
+ # echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
+
+ # echo 'disable_hist:net:netif_receive_skb if comm==wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
+
+ The above sets up an initially paused hist trigger which is unpaused
+ and starts aggregating events when a given program is executed, and
+ which stops aggregating when the process exits and the hist trigger
+ is paused again.
+
+ The examples below provide a more concrete illustration of the
+ concepts and typical usage patterns discussed above.
+
+
+6.2 'hist' trigger examples
+---------------------------
+
+ The first set of examples creates aggregations using the kmalloc
+ event. The fields that can be used for the hist trigger are listed
+ in the kmalloc event's format file:
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/format
+ name: kmalloc
+ ID: 374
+ format:
+ field:unsigned short common_type; offset:0; size:2; signed:0;
+ field:unsigned char common_flags; offset:2; size:1; signed:0;
+ field:unsigned char common_preempt_count; offset:3; size:1; signed:0;
+ field:int common_pid; offset:4; size:4; signed:1;
+
+ field:unsigned long call_site; offset:8; size:8; signed:0;
+ field:const void * ptr; offset:16; size:8; signed:0;
+ field:size_t bytes_req; offset:24; size:8; signed:0;
+ field:size_t bytes_alloc; offset:32; size:8; signed:0;
+ field:gfp_t gfp_flags; offset:40; size:4; signed:0;
+
+ We'll start by creating a hist trigger that generates a simple table
+ that lists the total number of bytes requested for each function in
+ the kernel that made one or more calls to kmalloc:
+
+ # echo 'hist:key=call_site:val=bytes_req' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ This tells the tracing system to create a 'hist' trigger using the
+ call_site field of the kmalloc event as the key for the table, which
+ just means that each unique call_site address will have an entry
+ created for it in the table. The 'val=bytes_req' parameter tells
+ the hist trigger that for each unique entry (call_site) in the
+ table, it should keep a running total of the number of bytes
+ requested by that call_site.
+
+ We'll let it run for awhile and then dump the contents of the 'hist'
+ file in the kmalloc event's subdirectory (for readability, a number
+ of entries have been omitted):
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active]
+
+ { call_site: 18446744072106379007 } hitcount: 1 bytes_req: 176
+ { call_site: 18446744071579557049 } hitcount: 1 bytes_req: 1024
+ { call_site: 18446744071580608289 } hitcount: 1 bytes_req: 16384
+ { call_site: 18446744071581827654 } hitcount: 1 bytes_req: 24
+ { call_site: 18446744071580700980 } hitcount: 1 bytes_req: 8
+ { call_site: 18446744071579359876 } hitcount: 1 bytes_req: 152
+ { call_site: 18446744071580795365 } hitcount: 3 bytes_req: 144
+ { call_site: 18446744071581303129 } hitcount: 3 bytes_req: 144
+ { call_site: 18446744071580713234 } hitcount: 4 bytes_req: 2560
+ { call_site: 18446744071580933750 } hitcount: 4 bytes_req: 736
+ .
+ .
+ .
+ { call_site: 18446744072106047046 } hitcount: 69 bytes_req: 5576
+ { call_site: 18446744071582116407 } hitcount: 73 bytes_req: 2336
+ { call_site: 18446744072106054684 } hitcount: 136 bytes_req: 140504
+ { call_site: 18446744072106224230 } hitcount: 136 bytes_req: 19584
+ { call_site: 18446744072106078074 } hitcount: 153 bytes_req: 2448
+ { call_site: 18446744072106062406 } hitcount: 153 bytes_req: 36720
+ { call_site: 18446744071582507929 } hitcount: 153 bytes_req: 37088
+ { call_site: 18446744072102520590 } hitcount: 273 bytes_req: 10920
+ { call_site: 18446744071582143559 } hitcount: 358 bytes_req: 716
+ { call_site: 18446744072106465852 } hitcount: 417 bytes_req: 56712
+ { call_site: 18446744072102523378 } hitcount: 485 bytes_req: 27160
+ { call_site: 18446744072099568646 } hitcount: 1676 bytes_req: 33520
+
+ Totals:
+ Hits: 4610
+ Entries: 45
+ Dropped: 0
+
+ The output displays a line for each entry, beginning with the key
+ specified in the trigger, followed by the value(s) also specified in
+ the trigger. At the beginning of the output is a line that displays
+ the trigger info, which can also be displayed by reading the
+ 'trigger' file:
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+ hist:keys=call_site:vals=bytes_req:sort=hitcount:size=2048 [active]
+
+ At the end of the output are a few lines that display the overall
+ totals for the run. The 'Hits' field shows the total number of
+ times the event trigger was hit, the 'Entries' field shows the total
+ number of used entries in the hash table, and the 'Dropped' field
+ shows the number of hits that were dropped because the number of
+ used entries for the run exceeded the maximum number of entries
+ allowed for the table (normally 0, but if not a hint that you may
+ want to increase the size of the table using the 'size' parameter).
+
+ Notice in the above output that there's an extra field, 'hitcount',
+ which wasn't specified in the trigger. Also notice that in the
+ trigger info output, there's a parameter, 'sort=hitcount', which
+ wasn't specified in the trigger either. The reason for that is that
+ every trigger implicitly keeps a count of the total number of hits
+ attributed to a given entry, called the 'hitcount'. That hitcount
+ information is explicitly displayed in the output, and in the
+ absence of a user-specified sort parameter, is used as the default
+ sort field.
+
+ The value 'hitcount' can be used in place of an explicit value in
+ the 'values' parameter if you don't really need to have any
+ particular field summed and are mainly interested in hit
+ frequencies.
+
+ To turn the hist trigger off, simply call up the trigger in the
+ command history and re-execute it with a '!' prepended:
+
+ # echo '!hist:key=call_site:val=bytes_req' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ Finally, notice that the call_site as displayed in the output above
+ isn't really very useful. It's an address, but normally addresses
+ are displayed in hex. To have a numeric field displayed as a hex
+ value, simply append '.hex' to the field name in the trigger:
+
+ # echo 'hist:key=call_site.hex:val=bytes_req' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site.hex:vals=bytes_req:sort=hitcount:size=2048 [active]
+
+ { call_site: ffffffffa026b291 } hitcount: 1 bytes_req: 433
+ { call_site: ffffffffa07186ff } hitcount: 1 bytes_req: 176
+ { call_site: ffffffff811ae721 } hitcount: 1 bytes_req: 16384
+ { call_site: ffffffff811c5134 } hitcount: 1 bytes_req: 8
+ { call_site: ffffffffa04a9ebb } hitcount: 1 bytes_req: 511
+ { call_site: ffffffff8122e0a6 } hitcount: 1 bytes_req: 12
+ { call_site: ffffffff8107da84 } hitcount: 1 bytes_req: 152
+ { call_site: ffffffff812d8246 } hitcount: 1 bytes_req: 24
+ { call_site: ffffffff811dc1e5 } hitcount: 3 bytes_req: 144
+ { call_site: ffffffffa02515e8 } hitcount: 3 bytes_req: 648
+ { call_site: ffffffff81258159 } hitcount: 3 bytes_req: 144
+ { call_site: ffffffff811c80f4 } hitcount: 4 bytes_req: 544
+ .
+ .
+ .
+ { call_site: ffffffffa06c7646 } hitcount: 106 bytes_req: 8024
+ { call_site: ffffffffa06cb246 } hitcount: 132 bytes_req: 31680
+ { call_site: ffffffffa06cef7a } hitcount: 132 bytes_req: 2112
+ { call_site: ffffffff8137e399 } hitcount: 132 bytes_req: 23232
+ { call_site: ffffffffa06c941c } hitcount: 185 bytes_req: 171360
+ { call_site: ffffffffa06f2a66 } hitcount: 185 bytes_req: 26640
+ { call_site: ffffffffa036a70e } hitcount: 265 bytes_req: 10600
+ { call_site: ffffffff81325447 } hitcount: 292 bytes_req: 584
+ { call_site: ffffffffa072da3c } hitcount: 446 bytes_req: 60656
+ { call_site: ffffffffa036b1f2 } hitcount: 526 bytes_req: 29456
+ { call_site: ffffffffa0099c06 } hitcount: 1780 bytes_req: 35600
+
+ Totals:
+ Hits: 4775
+ Entries: 46
+ Dropped: 0
+
+ Even that's only marginally more useful - while hex values do look
+ more like addresses, what users are typically more interested in
+ when looking at text addresses are the corresponding symbols
+ instead. To have an address displayed as symbolic value instead,
+ simply append '.sym' or '.sym-offset' to the field name in the
+ trigger:
+
+ # echo 'hist:key=call_site.sym:val=bytes_req' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=hitcount:size=2048 [active]
+
+ { call_site: [ffffffff810adcb9] syslog_print_all } hitcount: 1 bytes_req: 1024
+ { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8
+ { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7
+ { call_site: [ffffffff8154acbe] usb_alloc_urb } hitcount: 1 bytes_req: 192
+ { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7
+ { call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40
+ { call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128
+ { call_site: [ffffffff811febd5] fsnotify_alloc_group } hitcount: 2 bytes_req: 528
+ { call_site: [ffffffff81440f58] __tty_buffer_request_room } hitcount: 2 bytes_req: 2624
+ { call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 2 bytes_req: 96
+ { call_site: [ffffffffa05e19af] ieee80211_start_tx_ba_session [mac80211] } hitcount: 2 bytes_req: 464
+ { call_site: [ffffffff81672406] tcp_get_metrics } hitcount: 2 bytes_req: 304
+ { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128
+ { call_site: [ffffffff81089b05] sched_create_group } hitcount: 2 bytes_req: 1424
+ .
+ .
+ .
+ { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1185 bytes_req: 123240
+ { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 1185 bytes_req: 104280
+ { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 1402 bytes_req: 190672
+ { call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 1518 bytes_req: 146208
+ { call_site: [ffffffffa029070e] drm_vma_node_allow [drm] } hitcount: 1746 bytes_req: 69840
+ { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 2021 bytes_req: 792312
+ { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 2592 bytes_req: 145152
+ { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2629 bytes_req: 378576
+ { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2629 bytes_req: 3783248
+ { call_site: [ffffffff81325607] apparmor_file_alloc_security } hitcount: 5192 bytes_req: 10384
+ { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 5529 bytes_req: 110584
+ { call_site: [ffffffff8131ebf7] aa_alloc_task_context } hitcount: 21943 bytes_req: 702176
+ { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 55759 bytes_req: 5074265
+
+ Totals:
+ Hits: 109928
+ Entries: 71
+ Dropped: 0
+
+ Because the default sort key above is 'hitcount', the above shows a
+ the list of call_sites by increasing hitcount, so that at the bottom
+ we see the functions that made the most kmalloc calls during the
+ run. If instead we we wanted to see the top kmalloc callers in
+ terms of the number of bytes requested rather than the number of
+ calls, and we wanted the top caller to appear at the top, we can use
+ the 'sort' parameter, along with the 'descending' modifier:
+
+ # echo 'hist:key=call_site.sym:val=bytes_req:sort=bytes_req.descending' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site.sym:vals=bytes_req:sort=bytes_req.descending:size=2048 [active]
+
+ { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 2186 bytes_req: 3397464
+ { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1790 bytes_req: 712176
+ { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 8132 bytes_req: 513135
+ { call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 106 bytes_req: 440128
+ { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 2186 bytes_req: 314784
+ { call_site: [ffffffff812891ca] ext4_find_extent } hitcount: 2174 bytes_req: 208992
+ { call_site: [ffffffff811ae8e1] __kmalloc } hitcount: 8 bytes_req: 131072
+ { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 859 bytes_req: 116824
+ { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 1834 bytes_req: 102704
+ { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 972 bytes_req: 101088
+ { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl [drm] } hitcount: 972 bytes_req: 85536
+ { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 3333 bytes_req: 66664
+ { call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 209 bytes_req: 61632
+ .
+ .
+ .
+ { call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128
+ { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128
+ { call_site: [ffffffff812d8406] copy_semundo } hitcount: 2 bytes_req: 48
+ { call_site: [ffffffff81200ba6] inotify_new_group } hitcount: 1 bytes_req: 48
+ { call_site: [ffffffffa027121a] drm_getmagic [drm] } hitcount: 1 bytes_req: 48
+ { call_site: [ffffffff811e3a25] __seq_open_private } hitcount: 1 bytes_req: 40
+ { call_site: [ffffffff811c52f4] bprm_change_interp } hitcount: 2 bytes_req: 16
+ { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8
+ { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7
+ { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7
+
+ Totals:
+ Hits: 32133
+ Entries: 81
+ Dropped: 0
+
+ To display the offset and size information in addition to the symbol
+ name, just use 'sym-offset' instead:
+
+ # echo 'hist:key=call_site.sym-offset:val=bytes_req:sort=bytes_req.descending' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site.sym-offset:vals=bytes_req:sort=bytes_req.descending:size=2048 [active]
+
+ { call_site: [ffffffffa046041c] i915_gem_execbuffer2+0x6c/0x2c0 [i915] } hitcount: 4569 bytes_req: 3163720
+ { call_site: [ffffffffa0489a66] intel_ring_begin+0xc6/0x1f0 [i915] } hitcount: 4569 bytes_req: 657936
+ { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23+0x694/0x1020 [i915] } hitcount: 1519 bytes_req: 472936
+ { call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23+0x516/0x1020 [i915] } hitcount: 3050 bytes_req: 211832
+ { call_site: [ffffffff811e2a1b] seq_buf_alloc+0x1b/0x50 } hitcount: 34 bytes_req: 148384
+ { call_site: [ffffffffa04a580c] intel_crtc_page_flip+0xbc/0x870 [i915] } hitcount: 1385 bytes_req: 144040
+ { call_site: [ffffffff811ae8e1] __kmalloc+0x191/0x1b0 } hitcount: 8 bytes_req: 131072
+ { call_site: [ffffffffa0287592] drm_mode_page_flip_ioctl+0x282/0x360 [drm] } hitcount: 1385 bytes_req: 121880
+ { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc+0x32/0x100 [drm] } hitcount: 1848 bytes_req: 103488
+ { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state+0x2c/0xa0 [i915] } hitcount: 461 bytes_req: 62696
+ { call_site: [ffffffffa029070e] drm_vma_node_allow+0x2e/0xd0 [drm] } hitcount: 1541 bytes_req: 61640
+ { call_site: [ffffffff815f8d7b] sk_prot_alloc+0xcb/0x1b0 } hitcount: 57 bytes_req: 57456
+ .
+ .
+ .
+ { call_site: [ffffffff8109524a] alloc_fair_sched_group+0x5a/0x1a0 } hitcount: 2 bytes_req: 128
+ { call_site: [ffffffffa027b921] drm_vm_open_locked+0x31/0xa0 [drm] } hitcount: 3 bytes_req: 96
+ { call_site: [ffffffff8122e266] proc_self_follow_link+0x76/0xb0 } hitcount: 8 bytes_req: 96
+ { call_site: [ffffffff81213e80] load_elf_binary+0x240/0x1650 } hitcount: 3 bytes_req: 84
+ { call_site: [ffffffff8154bc62] usb_control_msg+0x42/0x110 } hitcount: 1 bytes_req: 8
+ { call_site: [ffffffffa00bf6fe] hidraw_send_report+0x7e/0x1a0 [hid] } hitcount: 1 bytes_req: 7
+ { call_site: [ffffffffa00bf1ca] hidraw_report_event+0x8a/0x120 [hid] } hitcount: 1 bytes_req: 7
+
+ Totals:
+ Hits: 26098
+ Entries: 64
+ Dropped: 0
+
+ We can also add multiple fields to the 'values' parameter. For
+ example, we might want to see the total number of bytes allocated
+ alongside bytes requested, and display the result sorted by bytes
+ allocated in a descending order:
+
+ # echo 'hist:keys=call_site.sym:values=bytes_req,bytes_alloc:sort=bytes_alloc.descending' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=call_site.sym:vals=bytes_req,bytes_alloc:sort=bytes_alloc.descending:size=2048 [active]
+
+ { call_site: [ffffffffa046041c] i915_gem_execbuffer2 [i915] } hitcount: 7403 bytes_req: 4084360 bytes_alloc: 5958016
+ { call_site: [ffffffff811e2a1b] seq_buf_alloc } hitcount: 541 bytes_req: 2213968 bytes_alloc: 2228224
+ { call_site: [ffffffffa0489a66] intel_ring_begin [i915] } hitcount: 7404 bytes_req: 1066176 bytes_alloc: 1421568
+ { call_site: [ffffffffa045e7c4] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 1565 bytes_req: 557368 bytes_alloc: 1037760
+ { call_site: [ffffffff8125847d] ext4_htree_store_dirent } hitcount: 9557 bytes_req: 595778 bytes_alloc: 695744
+ { call_site: [ffffffffa045e646] i915_gem_do_execbuffer.isra.23 [i915] } hitcount: 5839 bytes_req: 430680 bytes_alloc: 470400
+ { call_site: [ffffffffa04c4a3c] intel_plane_duplicate_state [i915] } hitcount: 2388 bytes_req: 324768 bytes_alloc: 458496
+ { call_site: [ffffffffa02911f2] drm_modeset_lock_crtc [drm] } hitcount: 3911 bytes_req: 219016 bytes_alloc: 250304
+ { call_site: [ffffffff815f8d7b] sk_prot_alloc } hitcount: 235 bytes_req: 236880 bytes_alloc: 240640
+ { call_site: [ffffffff8137e559] sg_kmalloc } hitcount: 557 bytes_req: 169024 bytes_alloc: 221760
+ { call_site: [ffffffffa00b7c06] hid_report_raw_event [hid] } hitcount: 9378 bytes_req: 187548 bytes_alloc: 206312
+ { call_site: [ffffffffa04a580c] intel_crtc_page_flip [i915] } hitcount: 1519 bytes_req: 157976 bytes_alloc: 194432
+ .
+ .
+ .
+ { call_site: [ffffffff8109bd3b] sched_autogroup_create_attach } hitcount: 2 bytes_req: 144 bytes_alloc: 192
+ { call_site: [ffffffff81097ee8] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
+ { call_site: [ffffffff8109524a] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
+ { call_site: [ffffffff81095225] alloc_fair_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
+ { call_site: [ffffffff81097ec2] alloc_rt_sched_group } hitcount: 2 bytes_req: 128 bytes_alloc: 128
+ { call_site: [ffffffff81213e80] load_elf_binary } hitcount: 3 bytes_req: 84 bytes_alloc: 96
+ { call_site: [ffffffff81079a2e] kthread_create_on_node } hitcount: 1 bytes_req: 56 bytes_alloc: 64
+ { call_site: [ffffffffa00bf6fe] hidraw_send_report [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8
+ { call_site: [ffffffff8154bc62] usb_control_msg } hitcount: 1 bytes_req: 8 bytes_alloc: 8
+ { call_site: [ffffffffa00bf1ca] hidraw_report_event [hid] } hitcount: 1 bytes_req: 7 bytes_alloc: 8
+
+ Totals:
+ Hits: 66598
+ Entries: 65
+ Dropped: 0
+
+ Finally, to finish off our kmalloc example, instead of simply having
+ the hist trigger display symbolic call_sites, we can have the hist
+ trigger additionally display the complete set of kernel stack traces
+ that led to each call_site. To do that, we simply use the special
+ value 'stacktrace' for the key parameter:
+
+ # echo 'hist:keys=stacktrace:values=bytes_req,bytes_alloc:sort=bytes_alloc' > \
+ /sys/kernel/debug/tracing/events/kmem/kmalloc/trigger
+
+ The above trigger will use the kernel stack trace in effect when an
+ event is triggered as the key for the hash table. This allows the
+ enumeration of every kernel callpath that led up to a particular
+ event, along with a running total of any of the event fields for
+ that event. Here we tally bytes requested and bytes allocated for
+ every callpath in the system that led up to a kmalloc (in this case
+ every callpath to a kmalloc for a kernel compile):
+
+ # cat /sys/kernel/debug/tracing/events/kmem/kmalloc/hist
+ # trigger info: hist:keys=stacktrace:vals=bytes_req,bytes_alloc:sort=bytes_alloc:size=2048 [active]
+
+ { stacktrace:
+ __kmalloc_track_caller+0x10b/0x1a0
+ kmemdup+0x20/0x50
+ hidraw_report_event+0x8a/0x120 [hid]
+ hid_report_raw_event+0x3ea/0x440 [hid]
+ hid_input_report+0x112/0x190 [hid]
+ hid_irq_in+0xc2/0x260 [usbhid]
+ __usb_hcd_giveback_urb+0x72/0x120
+ usb_giveback_urb_bh+0x9e/0xe0
+ tasklet_hi_action+0xf8/0x100
+ __do_softirq+0x114/0x2c0
+ irq_exit+0xa5/0xb0
+ do_IRQ+0x5a/0xf0
+ ret_from_intr+0x0/0x30
+ cpuidle_enter+0x17/0x20
+ cpu_startup_entry+0x315/0x3e0
+ rest_init+0x7c/0x80
+ } hitcount: 3 bytes_req: 21 bytes_alloc: 24
+ { stacktrace:
+ __kmalloc_track_caller+0x10b/0x1a0
+ kmemdup+0x20/0x50
+ hidraw_report_event+0x8a/0x120 [hid]
+ hid_report_raw_event+0x3ea/0x440 [hid]
+ hid_input_report+0x112/0x190 [hid]
+ hid_irq_in+0xc2/0x260 [usbhid]
+ __usb_hcd_giveback_urb+0x72/0x120
+ usb_giveback_urb_bh+0x9e/0xe0
+ tasklet_hi_action+0xf8/0x100
+ __do_softirq+0x114/0x2c0
+ irq_exit+0xa5/0xb0
+ do_IRQ+0x5a/0xf0
+ ret_from_intr+0x0/0x30
+ } hitcount: 3 bytes_req: 21 bytes_alloc: 24
+ { stacktrace:
+ kmem_cache_alloc_trace+0xeb/0x150
+ aa_alloc_task_context+0x27/0x40
+ apparmor_cred_prepare+0x1f/0x50
+ security_prepare_creds+0x16/0x20
+ prepare_creds+0xdf/0x1a0
+ SyS_capset+0xb5/0x200
+ system_call_fastpath+0x12/0x6a
+ } hitcount: 1 bytes_req: 32 bytes_alloc: 32
+ .
+ .
+ .
+ { stacktrace:
+ __kmalloc+0x11b/0x1b0
+ i915_gem_execbuffer2+0x6c/0x2c0 [i915]
+ drm_ioctl+0x349/0x670 [drm]
+ do_vfs_ioctl+0x2f0/0x4f0
+ SyS_ioctl+0x81/0xa0
+ system_call_fastpath+0x12/0x6a
+ } hitcount: 17726 bytes_req: 13944120 bytes_alloc: 19593808
+ { stacktrace:
+ __kmalloc+0x11b/0x1b0
+ load_elf_phdrs+0x76/0xa0
+ load_elf_binary+0x102/0x1650
+ search_binary_handler+0x97/0x1d0
+ do_execveat_common.isra.34+0x551/0x6e0
+ SyS_execve+0x3a/0x50
+ return_from_execve+0x0/0x23
+ } hitcount: 33348 bytes_req: 17152128 bytes_alloc: 20226048
+ { stacktrace:
+ kmem_cache_alloc_trace+0xeb/0x150
+ apparmor_file_alloc_security+0x27/0x40
+ security_file_alloc+0x16/0x20
+ get_empty_filp+0x93/0x1c0
+ path_openat+0x31/0x5f0
+ do_filp_open+0x3a/0x90
+ do_sys_open+0x128/0x220
+ SyS_open+0x1e/0x20
+ system_call_fastpath+0x12/0x6a
+ } hitcount: 4766422 bytes_req: 9532844 bytes_alloc: 38131376
+ { stacktrace:
+ __kmalloc+0x11b/0x1b0
+ seq_buf_alloc+0x1b/0x50
+ seq_read+0x2cc/0x370
+ proc_reg_read+0x3d/0x80
+ __vfs_read+0x28/0xe0
+ vfs_read+0x86/0x140
+ SyS_read+0x46/0xb0
+ system_call_fastpath+0x12/0x6a
+ } hitcount: 19133 bytes_req: 78368768 bytes_alloc: 78368768
+
+ Totals:
+ Hits: 6085872
+ Entries: 253
+ Dropped: 0
+
+ If you key a hist trigger on common_pid, in order for example to
+ gather and display sorted totals for each process, you can use the
+ special .execname modifier to display the executable names for the
+ processes in the table rather than raw pids. The example below
+ keeps a per-process sum of total bytes read:
+
+ # echo 'hist:key=common_pid.execname:val=count:sort=count.descending' > \
+ /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/trigger
+
+ # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_read/hist
+ # trigger info: hist:keys=common_pid.execname:vals=count:sort=count.descending:size=2048 [active]
+
+ { common_pid: gnome-terminal [ 3196] } hitcount: 280 count: 1093512
+ { common_pid: Xorg [ 1309] } hitcount: 525 count: 256640
+ { common_pid: compiz [ 2889] } hitcount: 59 count: 254400
+ { common_pid: bash [ 8710] } hitcount: 3 count: 66369
+ { common_pid: dbus-daemon-lau [ 8703] } hitcount: 49 count: 47739
+ { common_pid: irqbalance [ 1252] } hitcount: 27 count: 27648
+ { common_pid: 01ifupdown [ 8705] } hitcount: 3 count: 17216
+ { common_pid: dbus-daemon [ 772] } hitcount: 10 count: 12396
+ { common_pid: Socket Thread [ 8342] } hitcount: 11 count: 11264
+ { common_pid: nm-dhcp-client. [ 8701] } hitcount: 6 count: 7424
+ { common_pid: gmain [ 1315] } hitcount: 18 count: 6336
+ .
+ .
+ .
+ { common_pid: postgres [ 1892] } hitcount: 2 count: 32
+ { common_pid: postgres [ 1891] } hitcount: 2 count: 32
+ { common_pid: gmain [ 8704] } hitcount: 2 count: 32
+ { common_pid: upstart-dbus-br [ 2740] } hitcount: 21 count: 21
+ { common_pid: nm-dispatcher.a [ 8696] } hitcount: 1 count: 16
+ { common_pid: indicator-datet [ 2904] } hitcount: 1 count: 16
+ { common_pid: gdbus [ 2998] } hitcount: 1 count: 16
+ { common_pid: rtkit-daemon [ 2052] } hitcount: 1 count: 8
+ { common_pid: init [ 1] } hitcount: 2 count: 2
+
+ Totals:
+ Hits: 2116
+ Entries: 51
+ Dropped: 0
+
+ Similarly, if you key a hist trigger on syscall id, for example to
+ gather and display a list of systemwide syscall hits, you can use
+ the special .syscall modifier to display the syscall names rather
+ than raw ids. The example below keeps a running total of syscall
+ counts for the system during the run:
+
+ # echo 'hist:key=id.syscall:val=hitcount' > \
+ /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
+
+ # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
+ # trigger info: hist:keys=id.syscall:vals=hitcount:sort=hitcount:size=2048 [active]
+
+ { id: sys_fsync [ 74] } hitcount: 1
+ { id: sys_newuname [ 63] } hitcount: 1
+ { id: sys_prctl [157] } hitcount: 1
+ { id: sys_statfs [137] } hitcount: 1
+ { id: sys_symlink [ 88] } hitcount: 1
+ { id: sys_sendmmsg [307] } hitcount: 1
+ { id: sys_semctl [ 66] } hitcount: 1
+ { id: sys_readlink [ 89] } hitcount: 3
+ { id: sys_bind [ 49] } hitcount: 3
+ { id: sys_getsockname [ 51] } hitcount: 3
+ { id: sys_unlink [ 87] } hitcount: 3
+ { id: sys_rename [ 82] } hitcount: 4
+ { id: unknown_syscall [ 58] } hitcount: 4
+ { id: sys_connect [ 42] } hitcount: 4
+ { id: sys_getpid [ 39] } hitcount: 4
+ .
+ .
+ .
+ { id: sys_rt_sigprocmask [ 14] } hitcount: 952
+ { id: sys_futex [202] } hitcount: 1534
+ { id: sys_write [ 1] } hitcount: 2689
+ { id: sys_setitimer [ 38] } hitcount: 2797
+ { id: sys_read [ 0] } hitcount: 3202
+ { id: sys_select [ 23] } hitcount: 3773
+ { id: sys_writev [ 20] } hitcount: 4531
+ { id: sys_poll [ 7] } hitcount: 8314
+ { id: sys_recvmsg [ 47] } hitcount: 13738
+ { id: sys_ioctl [ 16] } hitcount: 21843
+
+ Totals:
+ Hits: 67612
+ Entries: 72
+ Dropped: 0
+
+ The syscall counts above provide a rough overall picture of system
+ call activity on the system; we can see for example that the most
+ popular system call on this system was the 'sys_ioctl' system call.
+
+ We can use 'compound' keys to refine that number and provide some
+ further insight as to which processes exactly contribute to the
+ overall ioctl count.
+
+ The command below keeps a hitcount for every unique combination of
+ system call id and pid - the end result is essentially a table
+ that keeps a per-pid sum of system call hits. The results are
+ sorted using the system call id as the primary key, and the
+ hitcount sum as the secondary key:
+
+ # echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount' > \
+ /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
+
+ # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
+ # trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 [active]
+
+ { id: sys_read [ 0], common_pid: rtkit-daemon [ 1877] } hitcount: 1
+ { id: sys_read [ 0], common_pid: gdbus [ 2976] } hitcount: 1
+ { id: sys_read [ 0], common_pid: console-kit-dae [ 3400] } hitcount: 1
+ { id: sys_read [ 0], common_pid: postgres [ 1865] } hitcount: 1
+ { id: sys_read [ 0], common_pid: deja-dup-monito [ 3543] } hitcount: 2
+ { id: sys_read [ 0], common_pid: NetworkManager [ 890] } hitcount: 2
+ { id: sys_read [ 0], common_pid: evolution-calen [ 3048] } hitcount: 2
+ { id: sys_read [ 0], common_pid: postgres [ 1864] } hitcount: 2
+ { id: sys_read [ 0], common_pid: nm-applet [ 3022] } hitcount: 2
+ { id: sys_read [ 0], common_pid: whoopsie [ 1212] } hitcount: 2
+ .
+ .
+ .
+ { id: sys_ioctl [ 16], common_pid: bash [ 8479] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: bash [ 3472] } hitcount: 12
+ { id: sys_ioctl [ 16], common_pid: gnome-terminal [ 3199] } hitcount: 16
+ { id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 1808
+ { id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 5580
+ .
+ .
+ .
+ { id: sys_waitid [247], common_pid: upstart-dbus-br [ 2690] } hitcount: 3
+ { id: sys_waitid [247], common_pid: upstart-dbus-br [ 2688] } hitcount: 16
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 975] } hitcount: 2
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 3204] } hitcount: 4
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 2888] } hitcount: 4
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 3003] } hitcount: 4
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 2873] } hitcount: 4
+ { id: sys_inotify_add_watch [254], common_pid: gmain [ 3196] } hitcount: 6
+ { id: sys_openat [257], common_pid: java [ 2623] } hitcount: 2
+ { id: sys_eventfd2 [290], common_pid: ibus-ui-gtk3 [ 2760] } hitcount: 4
+ { id: sys_eventfd2 [290], common_pid: compiz [ 2994] } hitcount: 6
+
+ Totals:
+ Hits: 31536
+ Entries: 323
+ Dropped: 0
+
+ The above list does give us a breakdown of the ioctl syscall by
+ pid, but it also gives us quite a bit more than that, which we
+ don't really care about at the moment. Since we know the syscall
+ id for sys_ioctl (16, displayed next to the sys_ioctl name), we
+ can use that to filter out all the other syscalls:
+
+ # echo 'hist:key=id.syscall,common_pid.execname:val=hitcount:sort=id,hitcount if id == 16' > \
+ /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/trigger
+
+ # cat /sys/kernel/debug/tracing/events/raw_syscalls/sys_enter/hist
+ # trigger info: hist:keys=id.syscall,common_pid.execname:vals=hitcount:sort=id.syscall,hitcount:size=2048 if id == 16 [active]
+
+ { id: sys_ioctl [ 16], common_pid: gmain [ 2769] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: evolution-addre [ 8571] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: gmain [ 3003] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: gmain [ 2781] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: gmain [ 2829] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: bash [ 8726] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: bash [ 8508] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: gmain [ 2970] } hitcount: 1
+ { id: sys_ioctl [ 16], common_pid: gmain [ 2768] } hitcount: 1
+ .
+ .
+ .
+ { id: sys_ioctl [ 16], common_pid: pool [ 8559] } hitcount: 45
+ { id: sys_ioctl [ 16], common_pid: pool [ 8555] } hitcount: 48
+ { id: sys_ioctl [ 16], common_pid: pool [ 8551] } hitcount: 48
+ { id: sys_ioctl [ 16], common_pid: avahi-daemon [ 896] } hitcount: 66
+ { id: sys_ioctl [ 16], common_pid: Xorg [ 1267] } hitcount: 26674
+ { id: sys_ioctl [ 16], common_pid: compiz [ 2994] } hitcount: 73443
+
+ Totals:
+ Hits: 101162
+ Entries: 103
+ Dropped: 0
+
+ The above output shows that 'compiz' and 'Xorg' are far and away
+ the heaviest ioctl callers (which might lead to questions about
+ whether they really need to be making all those calls and to
+ possible avenues for further investigation.)
+
+ The compound key examples used a key and a sum value (hitcount) to
+ sort the output, but we can just as easily use two keys instead.
+ Here's an example where we use a compound key composed of the the
+ common_pid and size event fields. Sorting with pid as the primary
+ key and 'size' as the secondary key allows us to display an
+ ordered summary of the recvfrom sizes, with counts, received by
+ each process:
+
+ # echo 'hist:key=common_pid.execname,size:val=hitcount:sort=common_pid,size' > \
+ /sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/trigger
+
+ # cat /sys/kernel/debug/tracing/events/syscalls/sys_enter_recvfrom/hist
+ # trigger info: hist:keys=common_pid.execname,size:vals=hitcount:sort=common_pid.execname,size:size=2048 [active]
+
+ { common_pid: smbd [ 784], size: 4 } hitcount: 1
+ { common_pid: dnsmasq [ 1412], size: 4096 } hitcount: 672
+ { common_pid: postgres [ 1796], size: 1000 } hitcount: 6
+ { common_pid: postgres [ 1867], size: 1000 } hitcount: 10
+ { common_pid: bamfdaemon [ 2787], size: 28 } hitcount: 2
+ { common_pid: bamfdaemon [ 2787], size: 14360 } hitcount: 1
+ { common_pid: compiz [ 2994], size: 8 } hitcount: 1
+ { common_pid: compiz [ 2994], size: 20 } hitcount: 11
+ { common_pid: gnome-terminal [ 3199], size: 4 } hitcount: 2
+ { common_pid: firefox [ 8817], size: 4 } hitcount: 1
+ { common_pid: firefox [ 8817], size: 8 } hitcount: 5
+ { common_pid: firefox [ 8817], size: 588 } hitcount: 2
+ { common_pid: firefox [ 8817], size: 628 } hitcount: 1
+ { common_pid: firefox [ 8817], size: 6944 } hitcount: 1
+ { common_pid: firefox [ 8817], size: 408880 } hitcount: 2
+ { common_pid: firefox [ 8822], size: 8 } hitcount: 2
+ { common_pid: firefox [ 8822], size: 160 } hitcount: 2
+ { common_pid: firefox [ 8822], size: 320 } hitcount: 2
+ { common_pid: firefox [ 8822], size: 352 } hitcount: 1
+ .
+ .
+ .
+ { common_pid: pool [ 8923], size: 1960 } hitcount: 10
+ { common_pid: pool [ 8923], size: 2048 } hitcount: 10
+ { common_pid: pool [ 8924], size: 1960 } hitcount: 10
+ { common_pid: pool [ 8924], size: 2048 } hitcount: 10
+ { common_pid: pool [ 8928], size: 1964 } hitcount: 4
+ { common_pid: pool [ 8928], size: 1965 } hitcount: 2
+ { common_pid: pool [ 8928], size: 2048 } hitcount: 6
+ { common_pid: pool [ 8929], size: 1982 } hitcount: 1
+ { common_pid: pool [ 8929], size: 2048 } hitcount: 1
+
+ Totals:
+ Hits: 2016
+ Entries: 224
+ Dropped: 0
+
+ The above example also illustrates the fact that although a compound
+ key is treated as a single entity for hashing purposes, the sub-keys
+ it's composed of can be accessed independently.
+
+ The next example uses a string field as the hash key and
+ demonstrates how you can manually pause and continue a hist trigger.
+ In this example, we'll aggregate fork counts and don't expect a
+ large number of entries in the hash table, so we'll drop it to a
+ much smaller number, say 256:
+
+ # echo 'hist:key=child_comm:val=hitcount:size=256' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
+
+ # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
+ # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active]
+
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: ibus-daemon } hitcount: 1
+ { child_comm: whoopsie } hitcount: 1
+ { child_comm: smbd } hitcount: 1
+ { child_comm: gdbus } hitcount: 1
+ { child_comm: kthreadd } hitcount: 1
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: evolution-alarm } hitcount: 2
+ { child_comm: Socket Thread } hitcount: 2
+ { child_comm: postgres } hitcount: 2
+ { child_comm: bash } hitcount: 3
+ { child_comm: compiz } hitcount: 3
+ { child_comm: evolution-sourc } hitcount: 4
+ { child_comm: dhclient } hitcount: 4
+ { child_comm: pool } hitcount: 5
+ { child_comm: nm-dispatcher.a } hitcount: 8
+ { child_comm: firefox } hitcount: 8
+ { child_comm: dbus-daemon } hitcount: 8
+ { child_comm: glib-pacrunner } hitcount: 10
+ { child_comm: evolution } hitcount: 23
+
+ Totals:
+ Hits: 89
+ Entries: 20
+ Dropped: 0
+
+ If we want to pause the hist trigger, we can simply append :pause to
+ the command that started the trigger. Notice that the trigger info
+ displays as [paused]:
+
+ # echo 'hist:key=child_comm:val=hitcount:size=256:pause' >> \
+ /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
+
+ # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
+ # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [paused]
+
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: kthreadd } hitcount: 1
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: gdbus } hitcount: 1
+ { child_comm: ibus-daemon } hitcount: 1
+ { child_comm: Socket Thread } hitcount: 2
+ { child_comm: evolution-alarm } hitcount: 2
+ { child_comm: smbd } hitcount: 2
+ { child_comm: bash } hitcount: 3
+ { child_comm: whoopsie } hitcount: 3
+ { child_comm: compiz } hitcount: 3
+ { child_comm: evolution-sourc } hitcount: 4
+ { child_comm: pool } hitcount: 5
+ { child_comm: postgres } hitcount: 6
+ { child_comm: firefox } hitcount: 8
+ { child_comm: dhclient } hitcount: 10
+ { child_comm: emacs } hitcount: 12
+ { child_comm: dbus-daemon } hitcount: 20
+ { child_comm: nm-dispatcher.a } hitcount: 20
+ { child_comm: evolution } hitcount: 35
+ { child_comm: glib-pacrunner } hitcount: 59
+
+ Totals:
+ Hits: 199
+ Entries: 21
+ Dropped: 0
+
+ To manually continue having the trigger aggregate events, append
+ :cont instead. Notice that the trigger info displays as [active]
+ again, and the data has changed:
+
+ # echo 'hist:key=child_comm:val=hitcount:size=256:cont' >> \
+ /sys/kernel/debug/tracing/events/sched/sched_process_fork/trigger
+
+ # cat /sys/kernel/debug/tracing/events/sched/sched_process_fork/hist
+ # trigger info: hist:keys=child_comm:vals=hitcount:sort=hitcount:size=256 [active]
+
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: dconf worker } hitcount: 1
+ { child_comm: kthreadd } hitcount: 1
+ { child_comm: gdbus } hitcount: 1
+ { child_comm: ibus-daemon } hitcount: 1
+ { child_comm: Socket Thread } hitcount: 2
+ { child_comm: evolution-alarm } hitcount: 2
+ { child_comm: smbd } hitcount: 2
+ { child_comm: whoopsie } hitcount: 3
+ { child_comm: compiz } hitcount: 3
+ { child_comm: evolution-sourc } hitcount: 4
+ { child_comm: bash } hitcount: 5
+ { child_comm: pool } hitcount: 5
+ { child_comm: postgres } hitcount: 6
+ { child_comm: firefox } hitcount: 8
+ { child_comm: dhclient } hitcount: 11
+ { child_comm: emacs } hitcount: 12
+ { child_comm: dbus-daemon } hitcount: 22
+ { child_comm: nm-dispatcher.a } hitcount: 22
+ { child_comm: evolution } hitcount: 35
+ { child_comm: glib-pacrunner } hitcount: 59
+
+ Totals:
+ Hits: 206
+ Entries: 21
+ Dropped: 0
+
+ The previous example showed how to start and stop a hist trigger by
+ appending 'pause' and 'continue' to the hist trigger command. A
+ hist trigger can also be started in a paused state by initially
+ starting the trigger with ':pause' appended. This allows you to
+ start the trigger only when you're ready to start collecting data
+ and not before. For example, you could start the trigger in a
+ paused state, then unpause it and do something you want to measure,
+ then pause the trigger again when done.
+
+ Of course, doing this manually can be difficult and error-prone, but
+ it is possible to automatically start and stop a hist trigger based
+ on some condition, via the enable_hist and disable_hist triggers.
+
+ For example, suppose we wanted to take a look at the relative
+ weights in terms of skb length for each callpath that leads to a
+ netif_receieve_skb event when downloading a decent-sized file using
+ wget.
+
+ First we set up an initially paused stacktrace trigger on the
+ netif_receive_skb event:
+
+ # echo 'hist:key=stacktrace:vals=len:pause' > \
+ /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
+
+ Next, we set up an 'enable_hist' trigger on the sched_process_exec
+ event, with an 'if filename==/usr/bin/wget' filter. The effect of
+ this new trigger is that it will 'unpause' the hist trigger we just
+ set up on netif_receive_skb if and only if it sees a
+ sched_process_exec event with a filename of '/usr/bin/wget'. When
+ that happens, all netif_receive_skb events are aggregated into a
+ hash table keyed on stacktrace:
+
+ # echo 'enable_hist:net:netif_receive_skb if filename==/usr/bin/wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
+
+ The aggregation continues until the netif_receive_skb is paused
+ again, which is what the following disable_hist event does by
+ creating a similar setup on the sched_process_exit event, using the
+ filter 'comm==wget':
+
+ # echo 'disable_hist:net:netif_receive_skb if comm==wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
+
+ Whenever a process exits and the comm field of the disable_hist
+ trigger filter matches 'comm==wget', the netif_receive_skb hist
+ trigger is disabled.
+
+ The overall effect is that netif_receive_skb events are aggregated
+ into the hash table for only the duration of the wget. Executing a
+ wget command and then listing the 'hist' file will display the
+ output generated by the wget command:
+
+ $ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz
+
+ # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist
+ # trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
+
+ { stacktrace:
+ __netif_receive_skb_core+0x46d/0x990
+ __netif_receive_skb+0x18/0x60
+ netif_receive_skb_internal+0x23/0x90
+ napi_gro_receive+0xc8/0x100
+ ieee80211_deliver_skb+0xd6/0x270 [mac80211]
+ ieee80211_rx_handlers+0xccf/0x22f0 [mac80211]
+ ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211]
+ ieee80211_rx+0x31d/0x900 [mac80211]
+ iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm]
+ iwl_rx_dispatch+0x8e/0xf0 [iwldvm]
+ iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi]
+ irq_thread_fn+0x20/0x50
+ irq_thread+0x11f/0x150
+ kthread+0xd2/0xf0
+ ret_from_fork+0x42/0x70
+ } hitcount: 85 len: 28884
+ { stacktrace:
+ __netif_receive_skb_core+0x46d/0x990
+ __netif_receive_skb+0x18/0x60
+ netif_receive_skb_internal+0x23/0x90
+ napi_gro_complete+0xa4/0xe0
+ dev_gro_receive+0x23a/0x360
+ napi_gro_receive+0x30/0x100
+ ieee80211_deliver_skb+0xd6/0x270 [mac80211]
+ ieee80211_rx_handlers+0xccf/0x22f0 [mac80211]
+ ieee80211_prepare_and_rx_handle+0x4e7/0xc40 [mac80211]
+ ieee80211_rx+0x31d/0x900 [mac80211]
+ iwlagn_rx_reply_rx+0x3db/0x6f0 [iwldvm]
+ iwl_rx_dispatch+0x8e/0xf0 [iwldvm]
+ iwl_pcie_irq_handler+0xe3c/0x12f0 [iwlwifi]
+ irq_thread_fn+0x20/0x50
+ irq_thread+0x11f/0x150
+ kthread+0xd2/0xf0
+ } hitcount: 98 len: 664329
+ { stacktrace:
+ __netif_receive_skb_core+0x46d/0x990
+ __netif_receive_skb+0x18/0x60
+ process_backlog+0xa8/0x150
+ net_rx_action+0x15d/0x340
+ __do_softirq+0x114/0x2c0
+ do_softirq_own_stack+0x1c/0x30
+ do_softirq+0x65/0x70
+ __local_bh_enable_ip+0xb5/0xc0
+ ip_finish_output+0x1f4/0x840
+ ip_output+0x6b/0xc0
+ ip_local_out_sk+0x31/0x40
+ ip_send_skb+0x1a/0x50
+ udp_send_skb+0x173/0x2a0
+ udp_sendmsg+0x2bf/0x9f0
+ inet_sendmsg+0x64/0xa0
+ sock_sendmsg+0x3d/0x50
+ } hitcount: 115 len: 13030
+ { stacktrace:
+ __netif_receive_skb_core+0x46d/0x990
+ __netif_receive_skb+0x18/0x60
+ netif_receive_skb_internal+0x23/0x90
+ napi_gro_complete+0xa4/0xe0
+ napi_gro_flush+0x6d/0x90
+ iwl_pcie_irq_handler+0x92a/0x12f0 [iwlwifi]
+ irq_thread_fn+0x20/0x50
+ irq_thread+0x11f/0x150
+ kthread+0xd2/0xf0
+ ret_from_fork+0x42/0x70
+ } hitcount: 934 len: 5512212
+
+ Totals:
+ Hits: 1232
+ Entries: 4
+ Dropped: 0
+
+ The above shows all the netif_receive_skb callpaths and their total
+ lengths for the duration of the wget command.
+
+ The 'clear' hist trigger param can be used to clear the hash table.
+ Suppose we wanted to try another run of the previous example but
+ this time also wanted to see the complete list of events that went
+ into the histogram. In order to avoid having to set everything up
+ again, we can just clear the histogram first:
+
+ # echo 'hist:key=stacktrace:vals=len:clear' >> \
+ /sys/kernel/debug/tracing/events/net/netif_receive_skb/trigger
+
+ Just to verify that it is in fact cleared, here's what we now see in
+ the hist file:
+
+ # cat /sys/kernel/debug/tracing/events/net/netif_receive_skb/hist
+ # trigger info: hist:keys=stacktrace:vals=len:sort=hitcount:size=2048 [paused]
+
+ Totals:
+ Hits: 0
+ Entries: 0
+ Dropped: 0
+
+ Since we want to see the detailed list of every netif_receive_skb
+ event occurring during the new run, which are in fact the same
+ events being aggregated into the hash table, we add some additional
+ 'enable_event' events to the triggering sched_process_exec and
+ sched_process_exit events as such:
+
+ # echo 'enable_event:net:netif_receive_skb if filename==/usr/bin/wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
+
+ # echo 'disable_event:net:netif_receive_skb if comm==wget' > \
+ /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
+
+ If you read the trigger files for the sched_process_exec and
+ sched_process_exit triggers, you should see two triggers for each:
+ one enabling/disabling the hist aggregation and the other
+ enabling/disabling the logging of events:
+
+ # cat /sys/kernel/debug/tracing/events/sched/sched_process_exec/trigger
+ enable_event:net:netif_receive_skb:unlimited if filename==/usr/bin/wget
+ enable_hist:net:netif_receive_skb:unlimited if filename==/usr/bin/wget
+
+ # cat /sys/kernel/debug/tracing/events/sched/sched_process_exit/trigger
+ enable_event:net:netif_receive_skb:unlimited if comm==wget
+ disable_hist:net:netif_receive_skb:unlimited if comm==wget
+
+ In other words, whenever either of the sched_process_exec or
+ sched_process_exit events is hit and matches 'wget', it enables or
+ disables both the histogram and the event log, and what you end up
+ with is a hash table and set of events just covering the specified
+ duration. Run the wget command again:
+
+ $ wget https://www.kernel.org/pub/linux/kernel/v3.x/patch-3.19.xz
+
+ Displaying the 'hist' file should show something similar to what you
+ saw in the last run, but this time you should also see the
+ individual events in the trace file:
+
+ # cat /sys/kernel/debug/tracing/trace
+
+ # tracer: nop
+ #
+ # entries-in-buffer/entries-written: 183/1426 #P:4
+ #
+ # _-----=> irqs-off
+ # / _----=> need-resched
+ # | / _---=> hardirq/softirq
+ # || / _--=> preempt-depth
+ # ||| / delay
+ # TASK-PID CPU# |||| TIMESTAMP FUNCTION
+ # | | | |||| | |
+ wget-15108 [000] ..s1 31769.606929: netif_receive_skb: dev=lo skbaddr=ffff88009c353100 len=60
+ wget-15108 [000] ..s1 31769.606999: netif_receive_skb: dev=lo skbaddr=ffff88009c353200 len=60
+ dnsmasq-1382 [000] ..s1 31769.677652: netif_receive_skb: dev=lo skbaddr=ffff88009c352b00 len=130
+ dnsmasq-1382 [000] ..s1 31769.685917: netif_receive_skb: dev=lo skbaddr=ffff88009c352200 len=138
+ ##### CPU 2 buffer started ####
+ irq/29-iwlwifi-559 [002] ..s. 31772.031529: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433d00 len=2948
+ irq/29-iwlwifi-559 [002] ..s. 31772.031572: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432200 len=1500
+ irq/29-iwlwifi-559 [002] ..s. 31772.032196: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433100 len=2948
+ irq/29-iwlwifi-559 [002] ..s. 31772.032761: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d433000 len=2948
+ irq/29-iwlwifi-559 [002] ..s. 31772.033220: netif_receive_skb: dev=wlan0 skbaddr=ffff88009d432e00 len=1500
+ .
+ .
+ .
--
2.8.0.rc3
next prev parent reply other threads:[~2016-04-20 19:31 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-04-20 19:29 [for-next][PATCH 00/30] tracing: Add features for event-fork and histograms Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 01/30] tracing: Rename check_ignore_pid() to ignore_this_task() Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 02/30] tracing: Use pid bitmap instead of a pid array for set_event_pid Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 03/30] tracing: Add infrastructure to allow set_event_pid to follow children Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 04/30] tracing: Update the documentation to describe "event-fork" option Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 05/30] tracing: Add lock-free tracing_map Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 06/30] tracing: Fix TRACING_MAP Kconfig Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 07/30] tracing: Update some tracing_map constants and comments Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 08/30] tracing: Add hist event trigger command Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 09/30] tracing: Add hist trigger support for multiple values (vals= param) Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 10/30] tracing: Add hist trigger support for compound keys Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 11/30] tracing: Add hist trigger support for user-defined sorting (sort= param) Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 12/30] tracing: Add hist trigger support for pausing and continuing a trace Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 13/30] tracing: Add hist trigger support for clearing " Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 14/30] tracing: Add hist trigger hex modifier for displaying numeric fields Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 15/30] tracing: Add hist trigger sym and sym-offset modifiers Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 16/30] tracing: Add hist trigger execname modifier Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 17/30] tracing: Add hist trigger syscall modifier Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 18/30] tracing: Add hist trigger support for stacktraces as keys Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 19/30] tracing: Support string type key properly Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 20/30] tracing: Remove restriction on string position in hist trigger keys Steven Rostedt
2016-04-20 19:29 ` [for-next][PATCH 21/30] tracing: Add enable_hist/disable_hist triggers Steven Rostedt
2016-04-20 19:30 ` Steven Rostedt [this message]
2016-04-20 19:30 ` [for-next][PATCH 23/30] tracing: Add support for multiple hist triggers per event Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 24/30] tracing: Add support for named triggers Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 25/30] tracing: Add support for named hist triggers Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 26/30] kselftests/ftrace : Add event trigger testcases Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 27/30] kselftests/ftrace: Add hist " Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 28/30] tracing: Add hist trigger log2 modifier Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 29/30] kselftests/ftrace: Add a test for log2 modifier of hist trigger Steven Rostedt
2016-04-20 19:30 ` [for-next][PATCH 30/30] tracing: Fix unsigned comparison to zero in hist trigger code Steven Rostedt
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20160420193029.799008992@goodmis.org \
--to=rostedt@goodmis.org \
--cc=akpm@linux-foundation.org \
--cc=linux-kernel@vger.kernel.org \
--cc=masami.hiramatsu.pt@hitachi.com \
--cc=mingo@kernel.org \
--cc=namhyung@kernel.org \
--cc=tom.zanussi@linux.intel.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.