Date: Wed, 15 Feb 2012 17:39:45 +0200 From: George Kontostanos <gkontos.mail@gmail.com> To: Pavlo <devgs@ukr.net> Cc: freebsd-fs@freebsd.org Subject: Re: ZFS and mem management Message-ID: <CA%2BdUSyqRd9DFhhAtQqU%2BVdmUz_kxqo=jSApoGOUd1Q9StrCkxA@mail.gmail.com> In-Reply-To: <41082.1329320114.6955040073494560768@ffe1.ukr.net> References: <70229.1329318412.9319724204137054208@ffe16.ukr.net> <CA%2BdUSyp1p07ERXaL-zLG4ibGB45c7VGBNH3ALL4ZXbXUbeEDiA@mail.gmail.com> <41082.1329320114.6955040073494560768@ffe1.ukr.net>
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2012/2/15 Pavlo <devgs@ukr.net>: > > > 2012/2/15 Pavlo <devgs@ukr.net>: >> >> >> >>>On 15/02/2012 13:39, Pavlo wrote: >>>> >> >>>> >> >> Unfortunately we can't afford disabling prefetch. It is too much >>>> >> >> of an>> overhead.>> >> Also I made some tests. I have process that maps file >>>> >> >> using mmap() and>> writes or reads first byte of each page of mapped file >>>> >> >> with some data.> >>>Note that ZFS is designed so that it interacts somewhat badly with >>>mmap() and other kernel services which rely on coherency between VM and >>>IO such as sendfile(). At the very best, you will have two in-kernel >>>copies of all data buffers used with such interfaces, but there have >>>been sporadic reports that there are other bugs with it. >>> >>>If you have a test server, I'd recommend you do the same test on UFS for >>>comparison. >> >> Was going to try this... Thanks for reply. >> _______________________________________________ >> freebsd-fs@freebsd.org mailing list >> http://lists.freebsd.org/mailman/listinfo/freebsd-fs >> To unsubscribe, send any mail to "freebsd-fs-unsubscribe@freebsd.org" > > Why do you think that disabling prefetch is an overhead? > > > -- > George Kontostanos > Aicom telecoms ltd > http://www.aisecure.net > > > > Well... not me though. System administrator >_> . I suppose because we have > a big IO traffic. Not for a highly random I/O environment. -- George Kontostanos Aicom telecoms ltd http://www.aisecure.net
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