linux-kernel - Re: [PATCH] perf jvmti: remove redundant jitdump line table entries

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Message-ID: <CAP-5=fUXP7OVEAX+u7-t8VZ9d8xq747kWgdvC_s7=wiHg7iBSw@mail.gmail.com>
Date:   Wed, 27 May 2020 11:08:24 -0700
From:   Ian Rogers <irogers@...gle.com>
To:     Nick Gasson <nick.gasson@....com>
Cc:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Stephane Eranian <eranian@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] perf jvmti: remove redundant jitdump line table entries

On Tue, May 26, 2020 at 10:40 PM Nick Gasson <nick.gasson@....com> wrote:
>
> On 05/27/20 13:03 PM, Ian Rogers wrote:
> >
> > Great result, thanks! I note there is a lack of symbolization when
> > benchmarking a few Java applications. I'll try to see if there's a
> > sensible resolution for those.
> >
>
> I noticed it loses information when the Hotspot code cache is
> resized. I've been working around that by setting
> -XX:InitialCodeCacheSize and -XX:ReservedCodeCacheSize to large
> values. Does this help in your case?

Thanks, I tried and also with Steve's patch:
https://lore.kernel.org/lkml/1590544271-125795-1-git-send-email-steve.maclean@linux.microsoft.com/

Trying something very basic like just the -version command with compile only:
/tmp/perf/perf record -k 1 -e cycles:u -F 6500 -o /tmp/perf.data java
-agentpath:/tmp/perf/libperf-jvmti.so -XX:+PreserveFramePointer
-XX:InitialCodeCacheSize=2G -XX:ReservedCodeCacheSize=2G
-XX:CompileOnly=1 -version
/tmp/perf/perf inject -i /tmp/perf.data -o /tmp/perf-jit.data -j
/tmp/perf/perf report -i /tmp/perf-jit.data

I don't see any of the JDK classes but 35 unknown symbols out of 272.
The JDK classes are stripped to some degree iirc, but we should be
able to give a symbol name as we don't care about local variables and
like.

This isn't a blocker for this patch and perhaps I'm special in seeing
this problem. Thanks,
Ian

> >
> > It'd be better to make this into two patches. Also on acme's perf/core
> > branch if possible:
> > https://git.kernel.org/pub/scm/linux/kernel/git/acme/linux.git/log/?h=perf/core
>
> OK sure, I'll do that.
>
> --
> Nick