linux-kernel - Re: [PATCH v1 2/6] perf trace: Ignore thread hashing in summary

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Date: Wed, 14 Feb 2024 10:27:02 -0800
From: Ian Rogers <irogers@...gle.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, 
	Namhyung Kim <namhyung@...nel.org>, Mark Rutland <mark.rutland@....com>, 
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, 
	Adrian Hunter <adrian.hunter@...el.com>, Oliver Upton <oliver.upton@...ux.dev>, 
	Yang Jihong <yangjihong1@...wei.com>, linux-kernel@...r.kernel.org, 
	linux-perf-users@...r.kernel.org, bpf@...r.kernel.org
Subject: Re: [PATCH v1 2/6] perf trace: Ignore thread hashing in summary

On Wed, Feb 14, 2024 at 9:25 AM Arnaldo Carvalho de Melo
<acme@...nel.org> wrote:
>
> On Tue, Feb 13, 2024 at 10:37:04PM -0800, Ian Rogers wrote:
> > Commit 91e467bc568f ("perf machine: Use hashtable for machine
> > threads") made the iteration of thread tids unordered. The perf trace
> > --summary output sorts and prints each hash bucket, rather than all
> > threads globally. Change this behavior by turn all threads into a
> > list, sort the list by number of trace events then by tids, finally
> > print the list. This also allows the rbtree in threads to be not
> > accessed outside of machine.
>
> Can you please provide a refresh of the output that is changed by your patch?

Hmm.. looks like perf trace record has broken and doesn't produce
output in newer perfs. It works on 6.5 and so a bisect is necessary.

Without record it is hard to be repeatable but here is a before:
```
$ perf trace -a --summary sleep 1 2>&1 |grep events
Summary of events:
process1 (976898), 10 events, 0.1%
process2 (79368), 2 events, 0.0%
process3 (3759625), 11 events, 0.1%
..
```
Note, see how the events 10, 2, 11 aren't sorted.

After:
```
$ perf trace -a --summary sleep 1 2>&1 |grep events
Summary of events:
process1 (3190), 2 events, 0.0%
process1 (3191), 2 events, 0.0%
process2 (3681), 2 events, 0.0%
process3 (4034), 2 events, 0.0%
process3 (4035), 2 events, 0.0%
..
```
I've anonymized the process names.

Thanks,
Ian

> - Arnaldo