Re: [PATCH] sched: Only migrate tasks due to interrupts on an idle CPU if prev and target CPUs share cache

[Mel Gorman]

On Fri, Dec 15, 2017 at 09:38:06PM +0100, Mike Galbraith wrote:
> On Fri, 2017-12-15 at 16:52 +0000, Mel Gorman wrote:
> > 
> > It's a small improvement...
> 
> From my log on corr.arch.suse.de (2x8 box)
> 
> 4.15.0.g2db767d-default
> Throughput 2665.88 MB/sec  8 clients  8 procs  max_latency=21.472 ms
> 4.15.0.g2db767d-default NO_WA_IDLE
> Throughput 3416.35 MB/sec  8 clients  8 procs  max_latency=9.825 ms
> 
> Not so small improvement.  WA_IDLE ripped corr up pretty bad, turning
> it off restored 4.4 performance.
> 

Sounds plausible. I expect it depends on the remote access latency as
well as whether the data gets prefetched fast enough.

-- 
Mel Gorman
SUSE Labs