Date: Wed, 15 Feb 2012 17:07:24 +0100 From: Kai Gallasch <gallasch@free.de> To: freebsd-fs@freebsd.org Subject: Re: ZFS and mem management Message-ID: <C82EC982-C587-4579-8DD7-01B97186E2D2@free.de> In-Reply-To: <jhgdsu$k7l$1@dough.gmane.org> References: <15861.1329298812.1414986334451204096@ffe12.ukr.net> <92617.1329301696.6338962447434776576@ffe5.ukr.net> <CA%2BdUSyqKoqrfD_cgsfupsuZRE0O6dH-4F1roLp_GFaeBKJkN-w@mail.gmail.com> <CA%2BdUSyoRyC5O4D8tQQ9iDH2E87P3cxW_Ay8b6FuvzzbORpSYhA@mail.gmail.com> <96280.1329309582.18313701080496209920@ffe5.ukr.net> <jhgdsu$k7l$1@dough.gmane.org>
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Am 15.02.2012 um 15:02 schrieb Ivan Voras: > On 15/02/2012 13:39, Pavlo wrote: >>=20 >>=20 >>=20 >> Unfortunately we can't afford disabling prefetch. It is too much of = an >> overhead. >>=20 >> 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. >=20 > 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. So best practice for running apache2 on FreeBSD ZFS is making sure = EnableMMAP and EnableSendfile are disabled in httpd.conf, right? (both are turned off by default) [httpd.conf] # EnableMMAP and EnableSendfile: On systems that support it,=20 # memory-mapping or the sendfile syscall is used to deliver # files. This usually improves server performance, but must # be turned off when serving from networked-mounted=20 # filesystems or if support for these functions is otherwise # broken on your system. # EnableMMAP off EnableSendfile off Kai.=
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