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Date: Fri, 12 Sep 2014 10:37:39 -0700
From: David Ahern <dsahern@gmail.com>
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To: Pawel Moll <pawel.moll@arm.com>,
        Richard Cochran <richardcochran@gmail.com>,
        Steven Rostedt <rostedt@goodmis.org>, Ingo Molnar <mingo@redhat.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Paul Mackerras <paulus@samba.org>,
        Arnaldo Carvalho de Melo <acme@kernel.org>,
        John Stultz <john.stultz@linaro.org>
CC: linux-kernel@vger.kernel.org, linux-api@vger.kernel.org
Subject: Re: [RFC 2/2] perf: Marker software event and ioctl
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On 9/12/14, 4:48 AM, Pawel Moll wrote:
> This patch adds a PERF_COUNT_SW_MARKER event type, which
> can be requested by user and a PERF_EVENT_IOC_MARKER
> ioctl command which will inject an event of said type into
> the perf buffer. The ioctl can take a zero-terminated
> string argument, similar to tracing_marker in ftrace,
> which will be kept in the "raw" field of the sample.
>
> The main use case for this is synchronisation of
> performance data generated in user space with the perf
> stream coming from the kernel. For example, the marker
> can be inserted by a JIT engine after it generated
> portion of the code, but before the code is executed
> for the first time, allowing the post-processor to
> pick the correct debugging information. Other example
> is a system profiling tool taking data from other
> sources than just perf, which generates a marker
> at the beginning at at the end of the session
> (also possibly periodically during the session) to
> synchronise kernel timestamps with clock values
> obtained in userspace (gtod or raw_monotonic).

Seems really similar to what I proposed in the past:

https://lkml.org/lkml/2011/2/27/159

Which was rejected.

David