Re: [PATCHSET 0/4] perf report: Support folded callchain output (v4)

From: Namhyung Kim
Date: Wed Nov 04 2015 - 10:35:21 EST

Hi Arnaldo and Brendan,

On Wed, Nov 04, 2015 at 11:51:31AM -0300, Arnaldo Carvalho de Melo wrote:
> Em Tue, Nov 03, 2015 at 10:02:32PM -0800, Brendan Gregg escreveu:
> > On Tue, Nov 3, 2015 at 5:54 PM, Namhyung Kim <namhyung@xxxxxxxxxx> wrote:
> > > Ah, makes sense. So it'd look like
> > > $ perf report --stdio -g folded,count,info -F none -s comm
> > > $ perf report --stdio -g folded,count,info -F none -s pid
> > > The output would be
> > > 809 swapper-0 cpu_bringup_and_idle;cpu_startup_entry;default_idle_call;arch_cpu_idle;default_idle;xen_hypercall_sched_op
> > Thanks, looks almost right: a couple of minor changes:
> > 1. If perf already has the precedent of "PID:comm", instead of my
> > "comm-PID", then maybe it should use "PID:comm" for perf consistency.
> > Doesn't make much difference to me.

Right. Actually I'd like to write it that way.. ;-)

> > 2. The second space, delimiting "PID:comm" (or comm) and the stack...
> > I'm nervous about using space as a delimiter any more than once, since
> > it can also appear in comm (eg, "java main") and frames (eg,
> > "JavaCalls::call_helper(JavaValue*, methodHandle*, JavaCallArguments*,
> > Thread*)" -- that's direct from "perf script"!). I'd consider making
> > it a semicolon:

Fair enough.

> > 809 swapper-0;cpu_bringup_and_idle;cpu_startup_entry;...
> > So the output is "value key", and key is a semicolon delimited stack
> > with an optional comm or PID:comm frame at the start.
> Agreed, but then, we can have some sort of default and also be able to,
> using -F, specify what are the fields we want, and in which order, and I
> liked your suggestion of being able to specify "-F none" and that mean
> no hist line to be produced.
> Likewise, the way that each callchain line should be formatted should be
> programmable via the command line, via the -g option, no? Then script
> writers could use it in a way that doesn't requires further processing,
> as Brendan showed.

Right. So '-s <key1>[,<key2>,...] -g info' can control which info is
displayed along with the callchains.

$ perf report -s comm,dso -g folded,count,info -F none
809 swapper;[kernel.vmlinux];cpu_bringup_and_idle;cpu_startup_entry;...

Note that the info part (swapper;[kernel.vmlinux]) is also separated
by a semicolon. But I think it's ok since it's controlled by command
line, so script can know how many entries will be.

> But yeah, the value is the semicolon delimited stack all the way to the
> comm/PID:comm if there are more than one or if the user asks it to be
> there via a -g keyword, all the other counts/info are just relative to
> that, CSV or whatever other delimiter the user asks it to, and space is
> not an option, as we know it can appear in the middle of a COMM:

Yes, I think that we should use a given separator (using -t option)
instead of hard-coded semicolon. Although it'd be rare, it seems
possible to use semicolons in the comm name too.


> [root@zoo ~]# perf report -s comm | grep '[a-zA-Z] [a-zA-Z]'
> # To display the header info, please use
> # --header/--header-only options.
> # Total Lost Samples: 0
> # Samples: 164K of event 'cycles:pp'
> # Event count (approx.): 34422160859
> 0.11% DOM Worker
> 0.10% JS Helper
> 0.01% Qt bearer threa
> 0.00% Socket Thread
> 0.00% dconf worker
> 0.00% JS Watchdog
> [root@zoo ~]#
> - Arnaldo
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