lkml.org 
[lkml]   [2011]   [Jul]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] [PATCH] perf: Attaching an event to a specific PMU
On 05.07.11 05:12:52, Ingo Molnar wrote:
>
> * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
>
> > > Overall, my approach improves the perf design. It adds a better
> > > and more intuitve access to perf from user space with clear and
> > > common methods and interfaces. Please let me know the concerns
> > > you have.
> >
> > Its redundant, this interface ship has sailed, its not going to
> > happen.
>
> Even if we had the choice, i don't see how a /dev based enumeration
> of PMUs is in any way better than a topologically attached set of
> PMUs in /sys.
>
> This kind of structure is nice in principle:
>
> # ls -l /dev/pmu/
> total 0
> crw-rw---- 1 root root 254, 5 Jul 8 2011 breakpoint
> crw-rw---- 1 root root 254, 4 Jul 8 2011 cpu
> crw-rw---- 1 root root 254, 6 Jul 8 2011 proto
> crw-rw---- 1 root root 254, 1 Jul 8 2011 software
> crw-rw---- 1 root root 254, 2 Jul 8 2011 tracepoint
>
> But it should be done in /sys/.

I have to learn yet why /dev is bad and /sys is good...

The system topology is always in /sys, also for device nodes. But we
can't get a device file descriptor from /sys. I doubt /sys is capable
to handle a device use count (need to be checked). We actually must
grab the pmu while attaching events to it. And, user space
implementation is must easier with /dev (see code in my previous
mail).

My patch also includes code that creates a device class. It is also
visible in /sys/class/pmu/*.
-Robert

--
Advanced Micro Devices, Inc.
Operating System Research Center



\
 
 \ /
  Last update: 2011-07-06 18:57    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site