Re: [RFC][PATCH 0/3] locking/mutex: Rewrite basic mutex

[Waiman Long]

On 08/25/2016 11:43 AM, Peter Zijlstra wrote:
> On Tue, Aug 23, 2016 at 06:13:43PM -0700, Jason Low wrote:
> > I tested this patch on an 8 socket system with the high_systime AIM7
> > workload with diskfs. The patch provided big performance improvements in
> > terms of throughput in the highly contended cases.
> >
> > -------------------------------------------------
> > |  users      | avg throughput | avg throughput |
> >                | without patch  | with patch     |
> > -------------------------------------------------
> > | 10 - 90     |   13,943 JPM   |   14,432 JPM   |
> > -------------------------------------------------
> > | 100 - 900   |   75,475 JPM   |  102,922 JPM   |
> > -------------------------------------------------
> > | 1000 - 1900 |   77,299 JPM   |  115,271 JPM   |
> > -------------------------------------------------
> >
> > Unfortunately, at 2000 users, the modified kernel locked up.
> >
> > # INFO: task reaim:<#>  blocked for more than 120 seconds.
> >
> > So something appears to be buggy.
> So with the previously given changes to reaim, I get the below results
> on my 4 socket Haswell with the new version of 1/3 (also below).
>
> I still need to update 3/3..
>
> Note that I think my reaim change wrecked the jobs/min calculation
> somehow, as it keeps increasing. I do think however that the numbers are
> comparable between runs, since they're wrecked the same way.

The performance data for the 2 kernels were roughly the same. This was 
what I had been expecting as there was no change in algorithm in how the 
slowpath was being handled. So I was surprised by Jason's result 
yesterday showing such a big difference.

Cheers,
Longman