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    [W:0.042 / U:0.228 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site