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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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