[lkml]   [2010]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
SubjectRe: [PATCH 1/5] perf: Disallow mmap() on per-task inherited events
On Tue, May 18, 2010 at 03:32:59PM +0200, Peter Zijlstra wrote:

> Since we now have working per-task-per-cpu events for a while,
> disallow mmap() on per-task inherited events. Those things were
> a performance problem anyway, and doing away with it allows
> us to optimize the buffer somewhat by assuming there is only a single
> writer.

This also disallows user-space access to hardware counter for this
event -- which is arguably OK, since doing the userspace read would
give a different answer to read() on the event fd, as the read() sums
up all the child counters for us. Nevertheless, I think this
side-effect is worth mentioning.


 \ /
  Last update: 2010-05-25 03:09    [W:0.093 / U:10.596 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site