On Wed, Feb 15, 2023 at 12:16:38PM +1100, Stephen Rothwell wrote:
> diff --cc Documentation/trace/histogram.rst
> index 7b7e4893b8f6,8e95295e39b6..000000000000
> --- a/Documentation/trace/histogram.rst
> +++ b/Documentation/trace/histogram.rst
> @@@ -1861,9 -1864,9 +1864,9 @@@ A histogram can now be defined for the
> The above shows the latency "lat" in a power of 2 grouping.
>
> Like any other event, once a histogram is enabled for the event, the
> - output can be displayed by reading the event's 'hist' file.
> + output can be displayed by reading the event's 'hist' file::
>
> - # cat /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/hist
> + # cat /sys/kernel/tracing/events/synthetic/wakeup_latency/hist
>
> # event histogram
> #
> @@@ -1908,10 -1911,10 +1911,10 @@@
>
>
> The latency values can also be grouped linearly by a given size with
> - the ".buckets" modifier and specify a size (in this case groups of 10).
> + the ".buckets" modifier and specify a size (in this case groups of 10)::
>
> # echo 'hist:keys=pid,prio,lat.buckets=10:sort=lat' >> \
> - /sys/kernel/debug/tracing/events/synthetic/wakeup_latency/trigger
> + /sys/kernel/tracing/events/synthetic/wakeup_latency/trigger
>
> # event histogram
> #
> @@@ -2052,13 -2182,13 +2182,13 @@@ The following commonly-used handler.act
>
> # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\
> wakeup_new_test($testpid) if comm=="cyclictest"' >> \
> - /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> + /sys/kernel/tracing/events/sched/sched_wakeup_new/trigger
>
> - Or, equivalently, using the 'trace' keyword syntax:
> + Or, equivalently, using the 'trace' keyword syntax::
>
> - # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\
> - trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \
> - /sys/kernel/tracing/events/sched/sched_wakeup_new/trigger
> + # echo 'hist:keys=$testpid:testpid=pid:onmatch(sched.sched_wakeup_new).\
> + trace(wakeup_new_test,$testpid) if comm=="cyclictest"' >> \
> - /sys/kernel/debug/tracing/events/sched/sched_wakeup_new/trigger
> ++ /sys/kernel/tracing/events/sched/sched_wakeup_new/trigger
>
> Creating and displaying a histogram based on those events is now
> just a matter of using the fields and new synthetic event in the
> @@@ -2191,48 -2321,48 +2321,48 @@@
> resulting latency, stored in wakeup_lat, exceeds the current
> maximum latency, a snapshot is taken. As part of the setup, all
> the scheduler events are also enabled, which are the events that
> - will show up in the snapshot when it is taken at some point:
> + will show up in the snapshot when it is taken at some point::
>
> - # echo 1 > /sys/kernel/tracing/events/sched/enable
> - # echo 1 > /sys/kernel/debug/tracing/events/sched/enable
> ++ # echo 1 > /sys/kernel/tracing/events/sched/enable
>
> - # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
> - if comm=="cyclictest"' >> \
> - /sys/kernel/tracing/events/sched/sched_waking/trigger
> + # echo 'hist:keys=pid:ts0=common_timestamp.usecs \
> + if comm=="cyclictest"' >> \
> - /sys/kernel/debug/tracing/events/sched/sched_waking/trigger
> ++ /sys/kernel/tracing/events/sched/sched_waking/trigger
>
> - # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0: \
> - onmax($wakeup_lat).save(next_prio,next_comm,prev_pid,prev_prio, \
> - prev_comm):onmax($wakeup_lat).snapshot() \
> - if next_comm=="cyclictest"' >> \
> - /sys/kernel/tracing/events/sched/sched_switch/trigger
> + # echo 'hist:keys=next_pid:wakeup_lat=common_timestamp.usecs-$ts0: \
> + onmax($wakeup_lat).save(next_prio,next_comm,prev_pid,prev_prio, \
> + prev_comm):onmax($wakeup_lat).snapshot() \
> + if next_comm=="cyclictest"' >> \
> - /sys/kernel/debug/tracing/events/sched/sched_switch/trigger
> ++ /sys/kernel/tracing/events/sched/sched_switch/trigger
>
> When the histogram is displayed, for each bucket the max value
> and the saved values corresponding to the max are displayed
> following the rest of the fields.
>
> If a snapshot was taken, there is also a message indicating that,
> - along with the value and event that triggered the global maximum:
> + along with the value and event that triggered the global maximum::
>
> - # cat /sys/kernel/tracing/events/sched/sched_switch/hist
> - { next_pid: 2101 } hitcount: 200
> - max: 52 next_prio: 120 next_comm: cyclictest \
> - prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
> - # cat /sys/kernel/debug/tracing/events/sched/sched_switch/hist
> ++ # cat /sys/kernel/tracing/events/sched/sched_switch/hist
> + { next_pid: 2101 } hitcount: 200
> + max: 52 next_prio: 120 next_comm: cyclictest \
> + prev_pid: 0 prev_prio: 120 prev_comm: swapper/6
>
> - { next_pid: 2103 } hitcount: 1326
> - max: 572 next_prio: 19 next_comm: cyclictest \
> - prev_pid: 0 prev_prio: 120 prev_comm: swapper/1
> + { next_pid: 2103 } hitcount: 1326
> + max: 572 next_prio: 19 next_comm: cyclictest \
> + prev_pid: 0 prev_prio: 120 prev_comm: swapper/1
>
> - { next_pid: 2102 } hitcount: 1982 \
> - max: 74 next_prio: 19 next_comm: cyclictest \
> - prev_pid: 0 prev_prio: 120 prev_comm: swapper/5
> + { next_pid: 2102 } hitcount: 1982 \
> + max: 74 next_prio: 19 next_comm: cyclictest \
> + prev_pid: 0 prev_prio: 120 prev_comm: swapper/5
>
> - Snapshot taken (see tracing/snapshot). Details:
> - triggering value { onmax($wakeup_lat) }: 572 \
> - triggered by event with key: { next_pid: 2103 }
> + Snapshot taken (see tracing/snapshot). Details:
> + triggering value { onmax($wakeup_lat) }: 572 \
> + triggered by event with key: { next_pid: 2103 }
>
> - Totals:
> - Hits: 3508
> - Entries: 3
> - Dropped: 0
> + Totals:
> + Hits: 3508
> + Entries: 3
> + Dropped: 0
>
> In the above case, the event that triggered the global maximum has
> the key with next_pid == 2103. If you look at the bucket that has
> @@@ -2310,15 -2440,15 +2440,15 @@@
> $cwnd variable. If the value has changed, a snapshot is taken.
> As part of the setup, all the scheduler and tcp events are also
> enabled, which are the events that will show up in the snapshot
> - when it is taken at some point:
> + when it is taken at some point::
>
> - # echo 1 > /sys/kernel/tracing/events/sched/enable
> - # echo 1 > /sys/kernel/tracing/events/tcp/enable
> - # echo 1 > /sys/kernel/debug/tracing/events/sched/enable
> - # echo 1 > /sys/kernel/debug/tracing/events/tcp/enable
> ++ # echo 1 > /sys/kernel/tracing/events/sched/enable
> ++ # echo 1 > /sys/kernel/tracing/events/tcp/enable
>
> - # echo 'hist:keys=dport:cwnd=snd_cwnd: \
> - onchange($cwnd).save(snd_wnd,srtt,rcv_wnd): \
> - onchange($cwnd).snapshot()' >> \
> - /sys/kernel/tracing/events/tcp/tcp_probe/trigger
> + # echo 'hist:keys=dport:cwnd=snd_cwnd: \
> + onchange($cwnd).save(snd_wnd,srtt,rcv_wnd): \
> + onchange($cwnd).snapshot()' >> \
> - /sys/kernel/debug/tracing/events/tcp/tcp_probe/trigger
> ++ /sys/kernel/tracing/events/tcp/tcp_probe/trigger
>
> When the histogram is displayed, for each bucket the tracked value
> and the saved values corresponding to that value are displayed
The resolution LGTM, thanks!
--
An old man doll... just what I always wanted! - Clara
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