From owner-freebsd-fs@FreeBSD.ORG  Wed Feb 15 16:35:13 2012
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From: Kai Gallasch <gallasch@free.de>
Date: Wed, 15 Feb 2012 17:07:24 +0100
To: freebsd-fs@freebsd.org
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Subject: Re: ZFS and mem management
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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.=