linux-kernel - Re: [PATCH] perf report: Skip symbols for idle symbols

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Date:   Tue, 18 Oct 2022 16:18:53 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     Rafał Miłecki <zajec5@...il.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        Rafał Miłecki <rafal@...ecki.pl>
Subject: Re: [PATCH] perf report: Skip symbols for idle symbols

Em Tue, Oct 18, 2022 at 02:54:07PM +0200, Rafał Miłecki escreveu:
> On 8.06.2022 07:51, Rafał Miłecki wrote:
> > From: Rafał Miłecki <rafal@...ecki.pl>
> > 
> > Displaying idle symbols is rather useless and makes reviewing "real"
> > symbols harder. perf top already skips them so perf report should
> > probably do the same.
> > 
> > BEFORE
> > 
> > # Overhead  Command          Shared Object          Symbol
> > # ........  ...............  .....................  ...................................
> > #
> >      75.04%  swapper          [kernel.kallsyms]      [k] arch_cpu_idle
> >       1.05%  ksoftirqd/0      [kernel.kallsyms]      [k] __pi___inval_dcache_area
> >       0.78%  ksoftirqd/0      [kernel.kallsyms]      [k] __netif_receive_skb_core
> >       0.75%  ksoftirqd/0      [kernel.kallsyms]      [k] fib_table_lookup
> >       0.58%  ksoftirqd/0      [kernel.kallsyms]      [k] __dev_queue_xmit
> >       0.56%  ksoftirqd/0      [kernel.kallsyms]      [k] bcm4908_enet_start_xmit
> >       0.55%  ksoftirqd/0      [kernel.kallsyms]      [k] __skb_flow_dissect
> >       0.53%  ksoftirqd/0      [kernel.kallsyms]      [k] __pi___clean_dcache_area_poc
> > 
> > AFTER
> > 
> > # Overhead  Command          Shared Object          Symbol
> > # ........  ...............  .....................  ...................................
> > #
> >       4.21%  ksoftirqd/0      [kernel.kallsyms]      [k] __pi___inval_dcache_area
> >       3.13%  ksoftirqd/0      [kernel.kallsyms]      [k] __netif_receive_skb_core
> >       3.01%  ksoftirqd/0      [kernel.kallsyms]      [k] fib_table_lookup
> >       2.32%  ksoftirqd/0      [kernel.kallsyms]      [k] __dev_queue_xmit
> >       2.23%  ksoftirqd/0      [kernel.kallsyms]      [k] bcm4908_enet_start_xmit
> >       2.21%  ksoftirqd/0      [kernel.kallsyms]      [k] __skb_flow_dissect
> >       2.13%  ksoftirqd/0      [kernel.kallsyms]      [k] __pi___clean_dcache_area_poc
> >       2.00%  ksoftirqd/0      [kernel.kallsyms]      [k] eth_type_trans
> >       1.86%  ksoftirqd/0      [kernel.kallsyms]      [k] bcm4908_enet_poll_rx
> >       1.73%  ksoftirqd/0      [kernel.kallsyms]      [k] __local_bh_enable_ip
> >       1.63%  ksoftirqd/0      [kernel.kallsyms]      [k] fib_rules_lookup
> >       1.61%  ksoftirqd/0      [kernel.kallsyms]      [k] bcm4908_enet_poll_tx
> >       (...)
> > 
> > Signed-off-by: Rafał Miłecki <rafal@...ecki.pl>
> 
> Ping? Does it look OK to you?

Its ok, but I wonder if after all those years changing this default
won't confuse users, so perhaps adding a 'I' hotkey to toggle showing
idle symbols?

Additionally having a 'perf config report.hide_idle=true' (for 'perf
top' as well), so that users can just switch to their liking?

Also add an entry to tools/perf/Documentation/tips.txt so that it
appears from time to time on the last line on the screen?

- Arnaldo