Re: [patch 0/3] [Announcement] Performance Counters for Linux

From: Andrew Morton
Date: Thu Dec 04 2008 - 22:31:20 EST

On Thu, 04 Dec 2008 23:44:39 -0000 Thomas Gleixner <tglx@xxxxxxxxxxxxx> wrote:

> Performance counters are special hardware registers available on most modern
> CPUs. These register count the number of certain types of hw events: such
> as instructions executed, cachemisses suffered, or branches mis-predicted,
> without slowing down the kernel or applications. These registers can also
> trigger interrupts when a threshold number of events have passed - and can
> thus be used to profile the code that runs on that CPU.
> We'd like to announce a brand new implementation of performance counter
> support for Linux. It is a very simple and extensible design that has the
> potential to implement the full range of features we would expect from such
> a subsystem.
> The Linux Performance Counter subsystem (implemented via the patches
> posted in this announcement) provides an abstraction of performance counter
> hardware capabilities. It provides per task and per CPU counters, and it
> provides event capabilities on top of those.
> The code is far from complete - but the basic approach is already there
> and stable.
> The biggest missing detail is lowlevel support for non-Intel CPUs and
> older Intel CPUs - right now the code is implemented for Intel Core2
> (and later) Intel CPUs that have the PERFMON CPU feature. (see below
> a wider list of missing/upcoming features)
> We are aware of the perfmon3 patchset that has been submitted to lkml
> recently. Our patchset tries to achieve a similar end result, with
> a fundamentally different (and we believe, superior :-) design:

There's also the perfctr patchset, which has been available for a long

I believe that established users of this sort of capability often
access it via the supposed-to-be-cross-platform PAPI interface/library.

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