Add an 'onmax(var).save(field,...)' hist trigger action which is invoked whenever an event exceeds the current maximum. The end result is that the trace event fields or variables specified as the onmax.save() params will be saved if 'var' exceeds the current maximum for that hist trigger entry. This allows context from the event that exhibited the new maximum to be saved for later reference. When the histogram is displayed, additional fields displaying the saved values will be printed. As an example the below defines a couple of hist triggers, one for sched_wakeup and another for sched_switch, keyed on pid. Whenever a sched_wakeup occurs, the timestamp is saved in the entry corresponding to the current pid, and when the scheduler switches back to that pid, the timestamp difference is calculated. If the resulting latency exceeds the current maximum latency, the specified save() values are saved: # echo 'hist:keys=pid:ts0=common_timestamp.usecs \ if comm=="cyclictest"' >> \ /sys/kernel/debug/tracing/events/sched/sched_wakeup/trigger # echo 'hist:keys=next_pid:\ wakeup_lat=common_timestamp.usecs-$ts0:\ onmax($wakeup_lat).save(next_comm,prev_pid,prev_prio,prev_comm) \ if next_comm=="cyclictest"' >> \ /sys/kernel/debug/tracing/events/sched/sched_switch/trigger When the histogram is displayed, the max value and the saved values corresponding to the max are displayed following the rest of the fields: # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist { next_pid: 3728 } hitcount: 199 \ max: 123 next_comm: cyclictest prev_pid: 0 \ prev_prio: 120 prev_comm: swapper/3 { next_pid: 3730 } hitcount: 1321 \ max: 15 next_comm: cyclictest prev_pid: 0 \ prev_prio: 120 prev_comm: swapper/1 { next_pid: 3729 } hitcount: 1973\ max: 25 next_comm: cyclictest prev_pid: 0 \ prev_prio: 120 prev_comm: swapper/0 Totals: Hits: 3493 Entries: 3 Dropped: 0 Link: http://lkml.kernel.org/r/006907f71b1e839bb059337ec3c496f84fcb71de.1516069914.git.tom.zanussi@linux.intel.com Signed-off-by: Tom Zanussi <tom.zanussi@linux.intel.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> |
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LICENSES | ||
arch | ||
block | ||
certs | ||
crypto | ||
drivers | ||
firmware | ||
fs | ||
include | ||
init | ||
ipc | ||
kernel | ||
lib | ||
mm | ||
net | ||
samples | ||
scripts | ||
security | ||
sound | ||
tools | ||
usr | ||
virt | ||
.cocciconfig | ||
.get_maintainer.ignore | ||
.gitattributes | ||
.gitignore | ||
.mailmap | ||
COPYING | ||
CREDITS | ||
Kbuild | ||
Kconfig | ||
MAINTAINERS | ||
Makefile | ||
README |
README
Linux kernel ============ This file was moved to Documentation/admin-guide/README.rst Please notice that there are several guides for kernel developers and users. These guides can be rendered in a number of formats, like HTML and PDF. In order to build the documentation, use ``make htmldocs`` or ``make pdfdocs``. There are various text files in the Documentation/ subdirectory, several of them using the Restructured Text markup notation. See Documentation/00-INDEX for a list of what is contained in each file. Please read the Documentation/process/changes.rst file, as it contains the requirements for building and running the kernel, and information about the problems which may result by upgrading your kernel.