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Date: Tue, 24 May 2011 09:59:25 -0400 (EDT)
From: Vince Weaver <vweaver1@eecs.utk.edu>
To: linux-kernel@vger.kernel.org
cc: Peter Zijlstra <a.p.zijlstra@chello.nl>, fbuihuu@gmail.com, mingo@elte.hu,
        paulus@samba.org, acme@redhat.com
Subject: perf: regression -- missing /sys/devices/system/cpu/perf_events
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I know this is a bit late, but for some reason our users sit on these 
things and then they aren't willing to take it up with linux-kernel 
themselves

> > > commit 15ac9a395a753cb28c674e7ea80386ffdff21785
> > > Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> > > Date:   Mon Sep 6 15:51:45 2010 +0200
> > > 
> > >    perf: Remove the sysfs bits

removed the /sys/devices/system/cpu/perf_events
I thought things in /sys were stable ABI?

Apparently it's common for people to have scripts to check if 
perf_events is available in a kernel by checking the existence of
/sys/devices/system/cpu/perf_events, even if they didn't use the
files within.

Now that 2.6.38 kernels are starting to hit the distros we're getting 
complaints that it's missing.

Vince