lkml.org 
[lkml]   [2018]   [Jul]   [19]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 08/10] psi: pressure stall information for CPU, memory, and IO
On Thu, Jul 19, 2018 at 11:26:14AM +0200, Peter Zijlstra wrote:
> On Wed, Jul 18, 2018 at 02:03:18PM +0200, Peter Zijlstra wrote:
>
> > Leaving us just 5 bytes short of needing a single cacheline :/
> >
> > struct ponies {
> > unsigned int tasks[3]; /* 0 12 */
> > unsigned int cpu_state:2; /* 12:30 4 */
> > unsigned int io_state:2; /* 12:28 4 */
> > unsigned int mem_state:2; /* 12:26 4 */
> >
> > /* XXX 26 bits hole, try to pack */
> >
> > /* typedef u64 */ long long unsigned int last_time; /* 16 8 */
> > /* typedef u64 */ long long unsigned int some_time[3]; /* 24 24 */
> > /* typedef u64 */ long long unsigned int full_time[2]; /* 48 16 */
> > /* --- cacheline 1 boundary (64 bytes) --- */
> > /* typedef u64 */ long long unsigned int nonidle_time; /* 64 8 */
> >
> > /* size: 72, cachelines: 2, members: 8 */
> > /* bit holes: 1, sum bit holes: 26 bits */
> > /* last cacheline: 8 bytes */
> > };
> >
> > ARGGH!
>
> It _might_ be possible to use curr->se.exec_start for last_time if you
> very carefully audit and place the hooks. I've not gone through it in
> detail, but it might just work.

Hnngg, and chop off an entire cacheline...

But don't we flush that delta out and update the timestamp on every
tick? entity_tick() does update_curr(). That might be too expensive :(

\
 
 \ /
  Last update: 2018-07-19 14:49    [W:0.096 / U:2.532 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site