linux-kernel - Re: [PATCH] perf report: show sort

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Message-ID: <20170314130416.GB3089@kernel.org>
Date:   Tue, 14 Mar 2017 10:04:16 -0300
From:   Arnaldo Carvalho de Melo <acme@...nel.org>
To:     "Du, Changbin" <changbin.du@...el.com>
Cc:     peterz@...radead.org, Namhyung Kim <namhyung@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>, Wang Nan <wangnan0@...wei.com>,
        David Ahern <dsahern@...il.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] perf report: show sort_order in title

Em Tue, Mar 14, 2017 at 10:16:44AM +0800, Du, Changbin escreveu:
> On Mon, Mar 13, 2017 at 11:57:18AM -0300, Arnaldo Carvalho de Melo wrote:
> > But then, while testing, 

> > Before:

> >   $ perf report
> >   Samples: 405  of event 'cycles', Event count (approx.): 101733003
> >   Overhead  Command          Shared Object                        Symbol
> >     11.15%  swapper          [kernel.vmlinux]                     [k] intel_idle

> >   Tip: Save output of perf stat using: perf stat record <target workload>

> > After:

> >   $ perf report
> >   Samples: 405  of event 'cycles', Event count (approx.): 101733003, Sort by: Children,Overhead,Command,Shared Object,Symbol
> >   Overhead  Command          Shared Object                        Symbol
> >     11.15%  swapper          [kernel.vmlinux]                     [k] intel_idle

> > I see now duplication of info, where is the value? Can you show the usecase in
> > a compelling way?
 
> Thanks for trying. The key idea is to show how does the data sort, especially
> the first sort key. When I use some GUI based perf tool, I can see how
> my data is sorted by checking the report header status. I think this is
> a good for browser.
 
> You are right, the info is duplicated. I got another idea that we show a '↓' at
> the header string and only for the first sort key. What do you think?
 
> $ perf report
>    Samples: 405  of event 'cycles', Event count (approx.): 101733003
>    ↓Overhead  Command          Shared Object                        Symbol

this is much more compact, but you need to make it abundantly clear what
you are trying to achieve by showind counter examples were what we get
on that line starting with your suggested marker isn't the sort order.
Otherwise even a character is one too much :-)

>      11.15%  swapper          [kernel.vmlinux]                     [k] intel_idle
>       3.00%  firefox          libxul.so                            [.] 0x0000000001298b8d
>       1.74%  swapper          [kernel.vmlinux]                     [k] update_blocked_averages

> Another idea I want to add is to support dynamic sorting. For me, I use perf to
> analysing entire system performance, and the data is very large. Then sometimes
> it take as long as ~10 minitues to read perf data. So I think if we can change
> sort w/o reload data will be good.

And in some cases it is even possible! I.e. if you haven't collapsed too
much, you will not have to reprocess the file to get to the new order.

BTW, have you played with:

  perf top --hierarchy

Try it with -g and --call-graph dwarf

Also try:

  perf report --hierarchy

- Arnaldo