* [PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty
2013-03-07 15:34 [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API Steven Rostedt
@ 2013-03-07 15:34 ` Steven Rostedt
2013-03-07 15:34 ` [PATCH 2/2] tracing: Do not return EINVAL in snapshot when not allocated Steven Rostedt
2013-03-08 7:32 ` [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API Hiraku Toyooka
2 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2013-03-07 15:34 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Frederic Weisbecker, Hiraku Toyooka
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From: "Steven Rostedt (Red Hat)" <srostedt@redhat.com>
When cat'ing the snapshot file, instead of showing an empty trace
header like the trace file does, show how to use the snapshot
feature.
Also, this is a good place to show if the snapshot has been allocated
or not. Users may want to "pre allocate" the snapshot to have a fast
"swap" of the current buffer. Otherwise, a swap would be slow and might
fail as it would need to allocate the snapshot buffer, and that might
fail under tight memory constraints.
Here's what it looked like before:
# tracer: nop
#
# entries-in-buffer/entries-written: 0/0 #P:4
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
Here's what it looks like now:
# tracer: nop
#
#
# * Snapshot is freed *
#
# Snapshot commands:
# echo 0 > snapshot : Clears and frees snapshot buffer
# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.
# Takes a snapshot of the main buffer.
# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)
# (Doesn't have to be '2' works with any number that
# is not a '0' or '1')
Acked-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 25 ++++++++++++++++++++++++-
1 file changed, 24 insertions(+), 1 deletion(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index c2e2c23..9e3120b 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -2400,6 +2400,27 @@ static void test_ftrace_alive(struct seq_file *m)
seq_printf(m, "# MAY BE MISSING FUNCTION EVENTS\n");
}
+#ifdef CONFIG_TRACER_MAX_TRACE
+static void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter)
+{
+ if (iter->trace->allocated_snapshot)
+ seq_printf(m, "#\n# * Snapshot is allocated *\n#\n");
+ else
+ seq_printf(m, "#\n# * Snapshot is freed *\n#\n");
+
+ seq_printf(m, "# Snapshot commands:\n");
+ seq_printf(m, "# echo 0 > snapshot : Clears and frees snapshot buffer\n");
+ seq_printf(m, "# echo 1 > snapshot : Allocates snapshot buffer, if not already allocated.\n");
+ seq_printf(m, "# Takes a snapshot of the main buffer.\n");
+ seq_printf(m, "# echo 2 > snapshot : Clears snapshot buffer (but does not allocate)\n");
+ seq_printf(m, "# (Doesn't have to be '2' works with any number that\n");
+ seq_printf(m, "# is not a '0' or '1')\n");
+}
+#else
+/* Should never be called */
+static inline void print_snapshot_help(struct seq_file *m, struct trace_iterator *iter) { }
+#endif
+
static int s_show(struct seq_file *m, void *v)
{
struct trace_iterator *iter = v;
@@ -2411,7 +2432,9 @@ static int s_show(struct seq_file *m, void *v)
seq_puts(m, "#\n");
test_ftrace_alive(m);
}
- if (iter->trace && iter->trace->print_header)
+ if (iter->snapshot && trace_empty(iter))
+ print_snapshot_help(m, iter);
+ else if (iter->trace && iter->trace->print_header)
iter->trace->print_header(m);
else
trace_default_header(m);
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread* [PATCH 2/2] tracing: Do not return EINVAL in snapshot when not allocated
2013-03-07 15:34 [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API Steven Rostedt
2013-03-07 15:34 ` [PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty Steven Rostedt
@ 2013-03-07 15:34 ` Steven Rostedt
2013-03-08 7:32 ` [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API Hiraku Toyooka
2 siblings, 0 replies; 6+ messages in thread
From: Steven Rostedt @ 2013-03-07 15:34 UTC (permalink / raw)
To: linux-kernel
Cc: Ingo Molnar, Andrew Morton, Frederic Weisbecker, Hiraku Toyooka
[-- Attachment #1: Type: text/plain, Size: 1294 bytes --]
From: "Steven Rostedt (Red Hat)" <srostedt@redhat.com>
To use the tracing snapshot feature, writing a '1' into the snapshot
file causes the snapshot buffer to be allocated if it has not already
been allocated and dose a 'swap' with the main buffer, so that the
snapshot now contains what was in the main buffer, and the main buffer
now writes to what was the snapshot buffer.
To free the snapshot buffer, a '0' is written into the snapshot file.
To clear the snapshot buffer, any number but a '0' or '1' is written
into the snapshot file. But if the file is not allocated it returns
-EINVAL error code. This is rather pointless. It is better just to
do nothing and return success.
Acked-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
---
kernel/trace/trace.c | 2 --
1 file changed, 2 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
index 9e3120b..1f835a8 100644
--- a/kernel/trace/trace.c
+++ b/kernel/trace/trace.c
@@ -4167,8 +4167,6 @@ tracing_snapshot_write(struct file *filp, const char __user *ubuf, size_t cnt,
default:
if (current_trace->allocated_snapshot)
tracing_reset_online_cpus(&max_tr);
- else
- ret = -EINVAL;
break;
}
--
1.7.10.4
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^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API
2013-03-07 15:34 [PATCH 0/2] [GIT PULL][3.9] tracing: Fix in snapshot API Steven Rostedt
2013-03-07 15:34 ` [PATCH 1/2] tracing: Add help of snapshot feature when snapshot is empty Steven Rostedt
2013-03-07 15:34 ` [PATCH 2/2] tracing: Do not return EINVAL in snapshot when not allocated Steven Rostedt
@ 2013-03-08 7:32 ` Hiraku Toyooka
2013-03-08 13:17 ` Ingo Molnar
2013-03-08 15:05 ` [tip:perf/urgent] tracing: update documentation of snapshot utility tip-bot for Hiraku Toyooka
2 siblings, 2 replies; 6+ messages in thread
From: Hiraku Toyooka @ 2013-03-08 7:32 UTC (permalink / raw)
To: Steven Rostedt
Cc: linux-kernel, Ingo Molnar, Andrew Morton, Frederic Weisbecker,
yrl.pp-manager.tt
Steven,
(03/08/2013 12:34 AM), Steven Rostedt wrote:
> The second patch, returns success on a reset of the buffer even if
> the buffer wasn't allocated. Returning -EINVAL is just confusing.
I realized we should update the snapshot documentation together with
this change.
I attached a patch to update the documentation. Could you include this
patch?
Thanks,
Hiraku Toyooka
From: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
Subject: [PATCH] tracing: update documentation of snapshot utility
Now, "snapshot" file returns success on a reset of snapshot buffer
even if the buffer wasn't allocated, instead of returning EINVAL.
This patch updates snapshot desctiption according to the change.
Signed-off-by: Hiraku Toyooka <hiraku.toyooka.gu@hitachi.com>
---
Documentation/trace/ftrace.txt | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/Documentation/trace/ftrace.txt b/Documentation/trace/ftrace.txt
index 53d6a3c..a372304 100644
--- a/Documentation/trace/ftrace.txt
+++ b/Documentation/trace/ftrace.txt
@@ -1873,7 +1873,7 @@ feature:
status\input | 0 | 1 | else |
--------------+------------+------------+------------+
- not allocated |(do nothing)| alloc+swap | EINVAL |
+ not allocated |(do nothing)| alloc+swap |(do nothing)|
--------------+------------+------------+------------+
allocated | free | swap | clear |
--------------+------------+------------+------------+
--
1.7.11.7
^ permalink raw reply related [flat|nested] 6+ messages in thread