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

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Date:   Wed, 15 Mar 2017 10:11:37 +0800
From:   "Du, Changbin" <changbin.du@...el.com>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>
Cc:     "Du, Changbin" <changbin.du@...el.com>, 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

On Tue, Mar 14, 2017 at 10:04:16AM -0300, Arnaldo Carvalho de Melo wrote:
> 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 :-)
> 
Yes, I just want get know how does perf data sort. Because sometimes the
real sort order doesn't match the '-s' option I given. In this case, I
was confused about the sorting before reading into the code.

> >      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

Sounds great! I tried '--hierarchy' option, but still don't know how to
resort the report. Could you give a hint?

-- 
Thanks,
Changbin Du

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