lkml.org 
[lkml]   [2014]   [Oct]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 09/11] perf/x86/intel: Implement LRU monitoring ID allocation for CQM
On Wed, 08 Oct, at 11:51:09AM, Peter Zijlstra wrote:
> On Wed, Sep 24, 2014 at 03:04:13PM +0100, Matt Fleming wrote:
> > From: Matt Fleming <matt.fleming@intel.com>
> >
> > It's possible to run into issues with re-using unused monitoring IDs
> > because there may be stale cachelines associated with that ID from a
> > previous allocation. This can cause the LLC occupancy values to be
> > inaccurate.
> >
> > To attempt to mitigate this problem we place the IDs on a least recently
> > used list, essentially a FIFO. The basic idea is that the longer the
> > time period between ID re-use the lower the probability that stale
> > cachelines exist in the cache.
>
> Do we want to provide a user configurable minumum guaranteed queue time?

Potentially, yeah. That might be better suited as part of the final
patch that includes the rotation code, which already has a delayed
workqueue.

We could add a minimum queue time before we start querying whether the
data occupancy value for an RMID has dropped to zero on all sockets.

That'd save us from an expensive smp_call_function_many() when we're
unlikely to succeed anyway.

--
Matt Fleming, Intel Open Source Technology Center


\
 
 \ /
  Last update: 2014-10-08 13:21    [W:0.119 / U:0.744 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site