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    SubjectRe: [PATCH 03/20] x86, mce: Add persistent MCE event

    * Borislav Petkov <bp@amd64.org> wrote:

    > On Wed, Nov 10, 2010 at 05:21:57PM -0500, Ingo Molnar wrote:
    > >
    > > * Ben Gamari <bgamari@gmail.com> wrote:
    > >
    > > > On Thu, 4 Nov 2010 16:36:39 +0100, Borislav Petkov <bp@amd64.org> wrote:
    > > > > From: Borislav Petkov <borislav.petkov@amd.com>
    > > > >
    > > > > Add the necessary glue to enable the mce_record tracepoint on boot
    > > > > turning it into a persistent event. This exports the MCE buffer
    > > > > read-only to a userspace daemon which will hook into it through debugfs
    > > > > when booting is finished.
    > > >
    > > > While MCE technically is a diagnostics service, do we want to start adding
    > > > dependencies on debugfs in long-running, common-place daemons? I was under the
    > > > impression we were to avoid using debugfs for anything other than values for
    > > > one-off debugging.
    > >
    > > See this current discussion thread on lkml:
    > >
    > > [RFC][PATCH] perf: sysfs type id
    > >
    > > Events are being added to sysfs as we want to avoid the debugfs dependency.
    >
    > Yep, event enumeration will land in /sysfs eventually but in this case debugfs is
    > used to export the buffers with the events recorded so far to the daemon which
    > mmaps them. And I remember also being mentioned that debugfs will thus be always
    > compiled in because of that.

    The event ring-buffer can be mmap()-ed off the fd that sys_perf_event_open() gives.
    This is what all of tools/perf/ does - it uses debugfs only for even enumeration
    (which will move to sysfs).

    Thanks,

    Ingo


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