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Date:      Fri, 17 Feb 2012 14:54:51 +0100
From:      Ivan Voras <ivoras@freebsd.org>
To:        freebsd-fs@freebsd.org
Subject:   Re: ZFS and mem management
Message-ID:  <jhlm7b$tge$1@dough.gmane.org>
In-Reply-To: <C82EC982-C587-4579-8DD7-01B97186E2D2@free.de>
References:  <15861.1329298812.1414986334451204096@ffe12.ukr.net> <92617.1329301696.6338962447434776576@ffe5.ukr.net> <CA%2BdUSyqKoqrfD_cgsfupsuZRE0O6dH-4F1roLp_GFaeBKJkN-w@mail.gmail.com> <CA%2BdUSyoRyC5O4D8tQQ9iDH2E87P3cxW_Ay8b6FuvzzbORpSYhA@mail.gmail.com> <96280.1329309582.18313701080496209920@ffe5.ukr.net> <jhgdsu$k7l$1@dough.gmane.org> <C82EC982-C587-4579-8DD7-01B97186E2D2@free.de>

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On 15/02/2012 17:07, Kai Gallasch wrote:
>=20
> Am 15.02.2012 um 15:02 schrieb Ivan Voras:
>=20
>> On 15/02/2012 13:39, Pavlo wrote:
>>>
>>>
>>>
>>> Unfortunately we can't afford disabling prefetch. It is too much of a=
n
>>> overhead.
>>>
>>> Also I made some tests. I have process that maps file using mmap() an=
d
>>> writes or reads first byte of each page of mapped file with some data=
=2E
>>
>> Note that ZFS is designed so that it interacts somewhat badly with
>> mmap() and other kernel services which rely on coherency between VM an=
d
>> 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.
>=20
> So best practice for running apache2 on FreeBSD ZFS is making sure Enab=
leMMAP and EnableSendfile are disabled in httpd.conf, right?

Yes.

> (both are turned off by default)

No, they are enabled by default:

http://httpd.apache.org/docs/2.2/mod/core.html#enablemmap



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