linux-kernel - Re: [RFC PATCH 27/30] Code tagging based latency tracking

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Date:   Thu, 1 Sep 2022 17:46:27 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, kent.overstreet@...ux.dev,
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Subject: Re: [RFC PATCH 27/30] Code tagging based latency tracking

On Thu, 1 Sep 2022 17:38:44 -0400
Steven Rostedt <rostedt@...dmis.org> wrote:

>  # echo 'hist:keys=comm,prio,delta.buckets=10:sort=delta' > /sys/kernel/tracing/events/synthetic/wakeup_lat/trigger

The above could almost be done with sqlhist (but I haven't implemented
"buckets=10" yet because that's a new feature. But for now, let's do log2):

 # sqlhist -e 'select comm,prio,cast(delta as log2) from wakeup_lat'

("-e" is to execute the command, as it normally only displays what commands
need to be run to create the synthetic events and histograms)

# cat /sys/kernel/tracing/events/synthetic/wakeup_lat/hist
# event histogram
#
# trigger info: hist:keys=comm,prio,delta.log2:vals=hitcount:sort=hitcount:size=2048 [active]
#

{ comm: migration/4                                       , prio:          0, delta: ~ 2^5  } hitcount:          1
{ comm: migration/0                                       , prio:          0, delta: ~ 2^4  } hitcount:          2
{ comm: rtkit-daemon                                      , prio:          0, delta: ~ 2^7  } hitcount:          2
{ comm: rtkit-daemon                                      , prio:          0, delta: ~ 2^6  } hitcount:          4
{ comm: migration/0                                       , prio:          0, delta: ~ 2^5  } hitcount:          8
{ comm: migration/4                                       , prio:          0, delta: ~ 2^4  } hitcount:          9
{ comm: migration/2                                       , prio:          0, delta: ~ 2^4  } hitcount:         10
{ comm: migration/5                                       , prio:          0, delta: ~ 2^4  } hitcount:         10
{ comm: migration/7                                       , prio:          0, delta: ~ 2^4  } hitcount:         10
{ comm: migration/1                                       , prio:          0, delta: ~ 2^4  } hitcount:         10
{ comm: migration/6                                       , prio:          0, delta: ~ 2^4  } hitcount:         10

Totals:
    Hits: 76
    Entries: 11
    Dropped: 0


-- Steve