ZFS and mem management

George Kontostanos gkontos.mail at gmail.com
Wed Feb 15 15:39:47 UTC 2012

2012/2/15 Pavlo <devgs at ukr.net>:
> 2012/2/15 Pavlo <devgs at ukr.net>:
>>>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.
>>>If you have a test server, I'd recommend you do the same test on UFS for
>> Was going to try this... Thanks for reply.
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> Why do you think that disabling prefetch is an overhead?
> --
> George Kontostanos
> Aicom telecoms ltd
> http://www.aisecure.net
> Well... not me though. System administrator >_> . I suppose because we have
> a big IO traffic.

Not for a highly random I/O environment.

George Kontostanos
Aicom telecoms ltd

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