Date: Sat, 23 Feb 2002 13:54:55 -0800 From: Terry Lambert <tlambert2@mindspring.com> To: Alfred Perlstein <alfred@FreeBSD.ORG> Cc: Matthew Dillon <dillon@apollo.backplane.com>, Seigo Tanimura <tanimura@r.dl.itc.u-tokyo.ac.jp>, current@FreeBSD.ORG, John Baldwin <jhb@FreeBSD.ORG> Subject: Re: How to fix malloc. Message-ID: <3C780FAF.F95A23EF@mindspring.com> References: <200201051752.g05Hq3gG074525@silver.carrots.uucp.r.dl.itc.u-tokyo.ac.jp> <XFMail.020114020307.jhb@FreeBSD.org> <200201241022.g0OAMISM093913@faber.r.dl.itc.u-tokyo.ac.jp> <20020124024534.V13686@elvis.mu.org> <200202131739.g1DHdZT5023794@rina.r.dl.itc.u-tokyo.ac.jp> <200202190945.g1J9j9kg076110@rina.r.dl.itc.u-tokyo.ac.jp> <200202232051.g1NKpE741310@apollo.backplane.com> <20020223211449.GJ80761@elvis.mu.org>
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Alfred Perlstein wrote: > All these per-subsystem free-lists are making me nervous in both > complexity and wasted code... Me too. > Ok, instead of keeping all these per-subsystem free-lists here's what > we do: > > In kern_malloc:free() right at the point of > if (size > MAXALLOCSAVE) we check if we have Giant or not. > if we do not then we simply queue the memory > however, if we do then we call into kmem_free with all the queued memory. > > This ought to solve the issue without making us keep all these > per-cpu caches. One modification: limit the number that are freed per invocation to some number small enough that there won't be a big latency. Once everything gets to this point, though, there will be nothing to trigger a free with giant held, and you'll just queue things up forever. Really, we need counted queues -- queues that know the number of elemenets on them. This is a requirement for RED-Queueing, and it will let us know when the queue gets deep... then you can grab giant, and flush down the queue if it hits a high watermark. Obviously, the correct way to handle this is per CPU memory pools that don't have any need for lock contention at all on the "real" frees. -- Terry To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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