linux-kernel - Re: [PATCH v8 0/9] rwsem performance optimizations

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Message-ID: <20131009072838.GY3081@twins.programming.kicks-ass.net>
Date:	Wed, 9 Oct 2013 09:28:38 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Tim Chen <tim.c.chen@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrea Arcangeli <aarcange@...hat.com>,
	Alex Shi <alex.shi@...aro.org>,
	Andi Kleen <andi@...stfloor.org>,
	Michel Lespinasse <walken@...gle.com>,
	Davidlohr Bueso <davidlohr.bueso@...com>,
	Matthew R Wilcox <matthew.r.wilcox@...el.com>,
	Dave Hansen <dave.hansen@...el.com>,
	Rik van Riel <riel@...hat.com>,
	Peter Hurley <peter@...leysoftware.com>,
	"Paul E.McKenney" <paulmck@...ux.vnet.ibm.com>,
	Jason Low <jason.low2@...com>,
	Waiman Long <Waiman.Long@...com>, linux-kernel@...r.kernel.org,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v8 0/9] rwsem performance optimizations

On Wed, Oct 09, 2013 at 08:15:51AM +0200, Ingo Molnar wrote:
> So I'd expect this to be a rather sensitive workload and you'd have to 
> actively engineer it to hit the effect PeterZ mentioned. I could imagine 
> MPI workloads to run into such patterns - but not deterministically.

The workload that I got the report from was a virus scanner, it would
spawn nr_cpus threads and {mmap file, scan content, munmap} through your
filesystem.

Now if I only could remember who reported this.. :/
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