Date: Mon, 06 Sep 2010 13:54:15 +0300 From: Andriy Gapon <avg@icyb.net.ua> To: Steven Hartland <killing@multiplay.co.uk> Cc: freebsd-fs@freebsd.org, jhell <jhell@DataIX.net> Subject: Re: zfs very poor performance compared to ufs due to lack of cache? Message-ID: <4C84C857.1070306@icyb.net.ua> In-Reply-To: <330B5DB2215F43899ABAEC2CF71C2EE0@multiplay.co.uk> References: <5DB6E7C798E44D33A05673F4B773405E@multiplay.co.uk><AANLkTi=6bta-Obrh2ejLCHENEbhV5stbMsvfek3Ki4ba@mail.gmail.com><4C825D65.3040004@DataIX.net> <7EA7AD058C0143B2BF2471CC121C1687@multiplay.co.uk> <1F64110BFBD5468B8B26879A9D8C94EF@multiplay.co.uk> <4C83A214.1080204@DataIX.net> <06B9D23F202D4DB88D69B7C4507986B7@multiplay.co.uk> <4C842905.2080602@DataIX.net> <330B5DB2215F43899ABAEC2CF71C2EE0@multiplay.co.uk>
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on 06/09/2010 02:57 Steven Hartland said the following: > Based on Jeremy's comments I'm updating the box the stable. Its building now > but will be the morning before I can reboot to activate changes as I need to > deactivate the stream instance and wait for all active connections to finish. > > That said the problem doesn't seem to be cache + free but more cache + free > + inactive with inactive being the large chunk, so not sure this change > would make any difference? > > How does ufs deal with this, does it take inactive into account? Seems a bit > silly for inactive pages to prevent reuse for extended periods when the > memory could be better used as cache. Inactive pages are also a cache, just a different kind. > As an experiment I compiled a little app which malloced a large block of > memory, 1.3G in this case and then freed it. This does indeed pull the memory > out of inactive and back into the free pool where zfs is which happy to > re-expand arc and once again cache large files. Seems a bit extreme to have to > do this though. > > Will see what happens with stable tomorrow though :) Don't forget the change that I suggested (from Artem's link). You may want to read the whole post too, I tried to explain what's going on with inactive and what the change tries to accomplish. -- Andriy Gapon
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