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

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Date:   Thu, 25 Aug 2016 12:33:04 -0400
From:   Waiman Long <waiman.long@....com>
To:     Peter Zijlstra <peterz@...radead.org>
CC:     Jason Low <jason.low2@....com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Ding Tianhong <dingtianhong@...wei.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Will Deacon <Will.Deacon@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Imre Deak <imre.deak@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        "Paul E. McKenney" <paulmck@...ibm.com>, <jason.low2@...com>
Subject: Re: [RFC][PATCH 0/3] locking/mutex: Rewrite basic mutex

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