From: Jiri Olsa <jolsa@redhat.com>
To: Steve MacLean <steve.maclean@linux.microsoft.com>
Cc: Steve MacLean <Steve.MacLean@microsoft.com>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>,
Mark Rutland <mark.rutland@arm.com>,
Alexander Shishkin <alexander.shishkin@linux.intel.com>,
Namhyung Kim <namhyung@kernel.org>,
Stephane Eranian <eranian@google.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND] perf inject --jit: Remove //anon mmap events
Date: Sat, 19 Oct 2019 19:49:00 +0200 [thread overview]
Message-ID: <20191019174900.GC12782@krava> (raw)
In-Reply-To: <1571336600-21843-1-git-send-email-steve.maclean@linux.microsoft.com>
On Thu, Oct 17, 2019 at 11:23:20AM -0700, Steve MacLean wrote:
> From: Steve MacLean <Steve.MacLean@Microsoft.com>
>
> While a JIT is jitting code it will eventually need to commit more pages and
> change these pages to executable permissions.
>
> Typically the JIT will want these colocated to minimize branch displacements.
>
> The kernel will coalesce these anonymous mapping with identical permissions
> before sending an MMAP event for the new pages. This means the mmap event for
> the new pages will include the older pages.
>
> These anonymous mmap events will obscure the jitdump injected pseudo events.
> This means that the jitdump generated symbols, machine code, debugging info,
> and unwind info will no longer be used.
>
> Observations:
>
> When a process emits a jit dump marker and a jitdump file, the perf-xxx.map
> file represents inferior information which has been superceded by the
> jitdump jit-xxx.dump file.
>
> Further the '//anon*' mmap events are only required for the legacy
> perf-xxx.map mapping.
>
> Summary:
>
> Add rbtree to track which pids have sucessfully injected a jitdump file.
>
> During "perf inject --jit", discard "//anon*" mmap events for any pid which
> has sucessfully processed a jitdump file.
>
> Committer testing:
>
> // jitdump case
> perf record <app with jitdump>
> perf inject --jit --input perf.data --output perfjit.data
>
> // verify mmap "//anon" events present initially
> perf script --input perf.data --show-mmap-events | grep '//anon'
> // verify mmap "//anon" events removed
> perf script --input perfjit.data --show-mmap-events | grep '//anon'
>
> // no jitdump case
> perf record <app without jitdump>
> perf inject --jit --input perf.data --output perfjit.data
>
> // verify mmap "//anon" events present initially
> perf script --input perf.data --show-mmap-events | grep '//anon'
> // verify mmap "//anon" events not removed
> perf script --input perfjit.data --show-mmap-events | grep '//anon'
>
> Repro:
>
> This issue was discovered while testing the initial CoreCLR jitdump
> implementation. https://github.com/dotnet/coreclr/pull/26897.
I posted some questions for previous version in here,
but can't find answers:
https://lore.kernel.org/lkml/20191003105716.GB23291@krava/
thanks,
jirka
prev parent reply other threads:[~2019-10-19 17:49 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-17 18:23 [PATCH RESEND] perf inject --jit: Remove //anon mmap events Steve MacLean
2019-10-19 17:49 ` Jiri Olsa [this message]
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