Date: Sun, 14 Jun 2009 14:01:43 +0100 From: Kris Kennaway <kris@FreeBSD.org> To: Attilio Rao <attilio@freebsd.org> Cc: freebsd-smp@freebsd.org, freebsd-arch@freebsd.org Subject: Re: [PATCH] Adaptive spinning for lockmgr Message-ID: <4A34F4B7.5050904@FreeBSD.org> In-Reply-To: <3bbf2fe10906081342i6ef418e0n75e22d0b9e2543b3@mail.gmail.com> References: <3bbf2fe10906081342i6ef418e0n75e22d0b9e2543b3@mail.gmail.com>
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Attilio Rao wrote: > This patch enables adaptive spinning for lockmgr: > http://www.freebsd.org/~attilio/adaptive_lockmgr.diff > > and it should presumably improve performance on disks/vfs/buffer cache > based benchmarks, so, if you want to try out and report any benchmarks > result, I'd love to see it. > Please note that there are some parameters to tune: for example, you > would like to not enable adaptive spinning to default while you just > want that for a class of locks (and in that case you want to apply the > reversed logic for what is living now) or you want to use different > values for retries and loops. Interested developers can refer to such > 3 variables. > Peter Holm alredy tested that patch for about 24hours without any > regression to report. > > Also note that the patch is not 100% yet as long as it needs UPDATES > and manpages updates, but they will be added just in time before to > commit. > The modify is all there. I have a vague memory that we had tested a version of this in the past and found that it caused a performance loss in common cases? Many lockmgr callers are not amenable to adaptive spinning because they have to wait on slow I/O. Testing only with e.g. md backing might give results that are non-representative. Kris
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