linux-kernel - RE: [EXTERNAL] Re: [PATCH v4] perf inject --jit: Remove //anon mmap events

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Date:   Fri, 29 May 2020 21:44:55 +0000
From:   Steve MacLean <Steve.MacLean@...rosoft.com>
To:     Steve MacLean <Steve.MacLean@...rosoft.com>,
        Ian Rogers <irogers@...gle.com>
CC:     Steve MacLean <steve.maclean@...ux.microsoft.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Stephane Eranian <eranian@...gle.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: RE: [EXTERNAL] Re: [PATCH v4] perf inject --jit: Remove //anon mmap
 events

>/tmp/perf/perf record -k 1 -e cycles:u -o /tmp/perf.data java 
>-agentpath:/tmp/perf/libperf-jvmti.so -XX:+PreserveFramePointer 
>-XX:InitialCodeCacheSize=20M -XX:ReservedCodeCacheSize=1G -jar 
>dacapo-9.12-bach.jar jython 

Its also possible the `InitialCodeCacheSize=20M` argument is masking the problem.  Something like 4K would make the problem much easier to see.

I see the problem every time .NET grows the cache across a 64K page boundary.  20M may mean you are allocating huge pages or something which might mask the problem. We may be allocating code pages 64K at a time.