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: >> >> >> >> 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. 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, # 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 # filesystems or if support for these functions is otherwise # broken on your system. # EnableMMAP off EnableSendfile off Kai.
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