From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: linux-kernel@vger.kernel.org
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
stable@vger.kernel.org, Ezequiel Garcia <elezegarcia@gmail.com>,
Steven Rostedt <rostedt@goodmis.org>
Subject: [ 35/40] ftrace: Update the kconfig for DYNAMIC_FTRACE
Date: Tue, 12 Mar 2013 15:43:56 -0700 [thread overview]
Message-ID: <20130312223215.231699728@linuxfoundation.org> (raw)
In-Reply-To: <20130312223211.492954675@linuxfoundation.org>
3.4-stable review patch. If anyone has any objections, please let me know.
------------------
From: Steven Rostedt <srostedt@redhat.com>
commit db05021d49a994ee40a9735d9c3cb0060c9babb8 upstream.
The prompt to enable DYNAMIC_FTRACE (the ability to nop and
enable function tracing at run time) had a confusing statement:
"enable/disable ftrace tracepoints dynamically"
This was written before tracepoints were added to the kernel,
but now that tracepoints have been added, this is very confusing
and has confused people enough to give wrong information during
presentations.
Not only that, I looked at the help text, and it still references
that dreaded daemon that use to wake up once a second to update
the nop locations and brick NICs, that hasn't been around for over
five years.
Time to bring the text up to the current decade.
Reported-by: Ezequiel Garcia <elezegarcia@gmail.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
kernel/trace/Kconfig | 24 ++++++++++++++----------
1 file changed, 14 insertions(+), 10 deletions(-)
--- a/kernel/trace/Kconfig
+++ b/kernel/trace/Kconfig
@@ -386,24 +386,28 @@ config KPROBE_EVENT
If you want to use perf tools, this option is strongly recommended.
config DYNAMIC_FTRACE
- bool "enable/disable ftrace tracepoints dynamically"
+ bool "enable/disable function tracing dynamically"
depends on FUNCTION_TRACER
depends on HAVE_DYNAMIC_FTRACE
default y
help
- This option will modify all the calls to ftrace dynamically
- (will patch them out of the binary image and replace them
- with a No-Op instruction) as they are called. A table is
- created to dynamically enable them again.
+ This option will modify all the calls to function tracing
+ dynamically (will patch them out of the binary image and
+ replace them with a No-Op instruction) on boot up. During
+ compile time, a table is made of all the locations that ftrace
+ can function trace, and this table is linked into the kernel
+ image. When this is enabled, functions can be individually
+ enabled, and the functions not enabled will not affect
+ performance of the system.
+
+ See the files in /sys/kernel/debug/tracing:
+ available_filter_functions
+ set_ftrace_filter
+ set_ftrace_notrace
This way a CONFIG_FUNCTION_TRACER kernel is slightly larger, but
otherwise has native performance as long as no tracing is active.
- The changes to the code are done by a kernel thread that
- wakes up once a second and checks to see if any ftrace calls
- were made. If so, it runs stop_machine (stops all CPUS)
- and modifies the code to jump over the call to ftrace.
-
config FUNCTION_PROFILER
bool "Kernel function profiler"
depends on FUNCTION_TRACER
next prev parent reply other threads:[~2013-03-12 22:43 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-12 22:43 [ 00/40] 3.4.36-stable review Greg Kroah-Hartman
2013-03-12 22:43 ` [ 01/40] ARM: VFP: fix emulation of second VFP instruction Greg Kroah-Hartman
2013-03-12 22:43 ` [ 02/40] ARM: fix scheduling while atomic warning in alignment handling code Greg Kroah-Hartman
2013-03-12 22:43 ` [ 03/40] xen/pci: We dont do multiple MSIs Greg Kroah-Hartman
2013-03-12 22:43 ` [ 04/40] SCSI: dc395x: uninitialized variable in device_alloc() Greg Kroah-Hartman
2013-03-12 22:43 ` [ 05/40] SCSI: storvsc: Initialize the sglist Greg Kroah-Hartman
2013-03-12 22:43 ` [ 06/40] target/pscsi: Fix page increment Greg Kroah-Hartman
2013-03-12 22:43 ` [ 07/40] btrfs: Init io_lock after cloning btrfs device struct Greg Kroah-Hartman
2013-03-12 22:43 ` [ 08/40] cifs: ensure that cifs_get_root() only traverses directories Greg Kroah-Hartman
2013-03-12 22:43 ` [ 09/40] NFS: Dont allow NFS silly-renamed files to be deleted, no signal Greg Kroah-Hartman
2013-03-12 22:43 ` [ 10/40] SUNRPC: Dont start the retransmission timer when out of socket space Greg Kroah-Hartman
2013-03-12 22:43 ` [ 11/40] ata_piix: reenable MS Virtual PC guests Greg Kroah-Hartman
2013-03-12 22:43 ` [ 12/40] hw_random: make buffer usable in scatterlist Greg Kroah-Hartman
2013-03-13 22:54 ` Satoru Takeuchi
2013-03-14 6:41 ` Rusty Russell
2013-03-14 13:24 ` [PATCH] hw_random: free rng_buffer at module exit Satoru Takeuchi
2013-03-15 5:05 ` Rusty Russell
2013-03-17 2:14 ` Ben Hutchings
2013-03-18 2:40 ` Rusty Russell
2013-03-20 0:29 ` Satoru Takeuchi
2013-03-12 22:43 ` [ 13/40] mwifiex: correct sleep delay counter Greg Kroah-Hartman
2013-03-12 22:43 ` [ 14/40] ath9k: fix RSSI dummy marker value Greg Kroah-Hartman
2013-03-12 22:43 ` [ 15/40] ath9k_hw: improve reset reliability after errors Greg Kroah-Hartman
2013-03-12 22:43 ` [ 16/40] md: protect against crash upon fsync on ro array Greg Kroah-Hartman
2013-03-12 22:43 ` [ 17/40] md: fix two bugs when attempting to resize RAID0 array Greg Kroah-Hartman
2013-03-12 22:43 ` [ 18/40] md: raid0: fix error return from create_stripe_zones Greg Kroah-Hartman
2013-03-12 22:43 ` [ 19/40] hwmon: (sht15) Check return value of regulator_enable() Greg Kroah-Hartman
2013-03-12 22:43 ` [ 20/40] hwmon: (pmbus/ltc2978) Fix peak attribute handling Greg Kroah-Hartman
2013-03-12 22:43 ` [ 21/40] hwmon: (pmbus/ltc2978) Use detected chip ID to select supported functionality Greg Kroah-Hartman
2013-03-12 22:43 ` [ 22/40] drm/radeon: add primary dac adj quirk for R200 board Greg Kroah-Hartman
2013-03-12 22:43 ` [ 23/40] ARM: 7663/1: perf: fix ARMv7 EVTYPE_MASK to include NSH bit Greg Kroah-Hartman
2013-03-12 22:43 ` [ 24/40] ALSA: ice1712: Initialize card->private_data properly Greg Kroah-Hartman
2013-03-12 22:43 ` [ 25/40] ALSA: vmaster: Fix slave change notification Greg Kroah-Hartman
2013-03-12 22:43 ` [ 26/40] e1000e: fix pci-device enable-counter balance Greg Kroah-Hartman
2013-03-12 22:43 ` [ 27/40] HID: logitech-dj: do not directly call hid_output_raw_report() during probe Greg Kroah-Hartman
2013-03-12 22:43 ` [ 28/40] xen/pat: Disable PAT using pat_enabled value Greg Kroah-Hartman
2013-03-12 22:43 ` [ 29/40] crypto: user - fix info leaks in report API Greg Kroah-Hartman
2013-03-12 22:43 ` [ 30/40] keys: fix race with concurrent install_user_keyrings() Greg Kroah-Hartman
2013-03-12 22:43 ` [ 31/40] Fix: compat_rw_copy_check_uvector() misuse in aio, readv, writev, and security keys Greg Kroah-Hartman
2013-03-12 22:43 ` [ 32/40] vfs: fix pipe counter breakage Greg Kroah-Hartman
2013-03-12 22:43 ` [ 33/40] rtc: rtc-mv: Add support for clk to avoid lockups Greg Kroah-Hartman
2013-03-12 23:08 ` Jason Cooper
2013-03-12 23:15 ` Greg Kroah-Hartman
2013-03-12 22:43 ` [ 34/40] Fix memory leak in cpufreq stats Greg Kroah-Hartman
2013-03-12 22:43 ` Greg Kroah-Hartman [this message]
2013-03-12 22:43 ` [ 36/40] dmi_scan: fix missing check for _DMI_ signature in smbios_present() Greg Kroah-Hartman
2013-03-12 22:43 ` [ 37/40] USB: Dont use EHCI port sempahore for USB 3.0 hubs Greg Kroah-Hartman
2013-03-12 22:43 ` [ 38/40] USB: Prepare for refactoring by adding extra udev checks Greg Kroah-Hartman
2013-03-12 22:44 ` [ 39/40] USB: Rip out recursive call on warm port reset Greg Kroah-Hartman
2013-03-12 22:44 ` [ 40/40] Revert "ALSA: hda - hdmi: Make jacks phantom, if theyre not detectable" Greg Kroah-Hartman
2013-03-13 3:57 ` [ 00/40] 3.4.36-stable review Shuah Khan
2013-03-14 13:39 ` Satoru Takeuchi
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