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Date: Tue, 18 Jun 2013 07:18:56 +0800 From: Alex Shi <alex.shi@...el.com> To: Tim Chen <tim.c.chen@...ux.intel.com> CC: Davidlohr Bueso <davidlohr.bueso@...com>, Ingo Molnar <mingo@...e.hu>, Rik van Riel <riel@...hat.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Andrea Arcangeli <aarcange@...hat.com>, Mel Gorman <mgorman@...e.de>, Andi Kleen <andi@...stfloor.org>, Andrew Morton <akpm@...ux-foundation.org>, Michel Lespinasse <walken@...gle.com>, "Wilcox, Matthew R" <matthew.r.wilcox@...el.com>, Dave Hansen <dave.hansen@...el.com>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org> Subject: Re: Performance regression from switching lock to rw-sem for anon-vma tree On 06/18/2013 02:45 AM, Tim Chen wrote: >>> + if (unlikely(sem->count < RWSEM_WAITING_BIAS)) { >>> > > + cpu_relax(); >>> > > + continue; >>> > > + } > The above two if statements could be cleaned up as a single check: > > if (unlikely(sem->count < RWSEM_WAITING_BIAS)) > return sem; > > This one statement is sufficient to check that we don't have a writer > stolen the lock before we attempt to acquire the read lock by modifying > sem->count. > > Thanks. I will send out the patchset base your suggestion. -- Thanks Alex -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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