Date: Mon, 17 Apr 2006 14:12:57 -0400 From: "Surer Dink" <surerlistmail@gmail.com> To: "Kris Kennaway" <kris@obsecurity.org>, smp@freebsd.org, current@freebsd.org Subject: Re: Anomalous performance increase from mutex profiling Message-ID: <b00a10c30604171112h392759d2h9be8ee656a7c18d8@mail.gmail.com> In-Reply-To: <20060417162216.GA90886@xor.obsecurity.org> References: <b00a10c30604170054r57d13768u4aeb79e91c436d51@mail.gmail.com> <20060417162216.GA90886@xor.obsecurity.org>
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On 4/17/06, Kris Kennaway <kris@obsecurity.org> wrote: > On Mon, Apr 17, 2006 at 03:54:07AM -0400, Surer Dink wrote: > > Please excuse if this is a stupid question - but might using MCS or > > QOLB locks in this situation be useful? > > What are they? Mellor-Crummy Scott: http://www.cs.rochester.edu/u/scott/papers/1991_ASPLOS_sync.pdf An overview comparing various possible optimizations for a few lock types, including MCS and QOLB: ftp://ftp.cs.utexas.edu/pub/dburger/papers/ISCA97_qolb.pdf I believe the QOLB proposal only suggested hardware modificaition for performance improvement, but could be implemented entirely in software - the overheads are high, but offer substantial performance benefit in high contention situations. MCS is based on QOSB, however fully implemented in software. There is also a proposal for changing lock to MCS dynamically, however I have not read it: ftp://ftp.cag.lcs.mit.edu/pub/papers/pdf/reactive.pdf
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