Message-ID: <1370231597.5988.79.camel@marge.simpson.net>
Subject: Re: [RFC PATCH] sched: smart wake-affine
From: Mike Galbraith <efault@gmx.de>
To: Michael Wang <wangyun@linux.vnet.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>, Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>, Alex Shi <alex.shi@intel.com>,
        Namhyung Kim <namhyung@kernel.org>, Paul Turner <pjt@google.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Nikunj A. Dadhania" <nikunj@linux.vnet.ibm.com>,
        Ram Pai <linuxram@us.ibm.com>
Date: Mon, 03 Jun 2013 05:53:17 +0200
In-Reply-To: <51AC0CD4.9070302@linux.vnet.ibm.com>
References: <51A43B16.9080801@linux.vnet.ibm.com>
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On Mon, 2013-06-03 at 11:26 +0800, Michael Wang wrote: 
> On 06/03/2013 11:09 AM, Mike Galbraith wrote:
> > On Mon, 2013-06-03 at 10:28 +0800, Michael Wang wrote: 
> >> On 05/28/2013 01:05 PM, Michael Wang wrote:
> >>> wake-affine stuff is always trying to pull wakee close to waker, by theory,
> >>> this will bring benefit if waker's cpu cached hot data for wakee, or the
> >>> extreme ping-pong case.
> >>>
> >>> And testing show it could benefit hackbench 15% at most.
> >>>
> >>> However, the whole stuff is somewhat blindly and time-consuming, some
> >>> workload therefore suffer.
> >>>
> >>> And testing show it could damage pgbench 50% at most.
> >>>
> >>> Thus, wake-affine stuff should be smarter, and realise when to stop
> >>> it's thankless effort.
> >>
> >> Is there any comments?
> > 
> > (I haven't had time to test-drive yet, -rt munches time like popcorn)
> 
> I see ;-)
> 
> During my testing, this one works well on the box, solved the issues of
> pgbench and won't harm hackbench any, I think we have caught some good
> point here :)

Some wider spectrum testing needs doing though.  Hackbench is a good
sign, but localhost and db type stuff that really suffer from misses
would be good to test.  Java crud tends to be sensitive too.  I used to
watch vmark (crap) as an indicator, if you see unhappiness there, you'll
very likely see it in other loads as well, it is very fond of cache
affine wakeups, but loathes preemption (super heavy loads usually do).

-Mike

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