Re: adding support for posix_fadvise()
От | Neil Conway |
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Тема | Re: adding support for posix_fadvise() |
Дата | |
Msg-id | 1067874283.3089.241.camel@tokyo обсуждение исходный текст |
Ответ на | Re: adding support for posix_fadvise() (Tom Lane <tgl@sss.pgh.pa.us>) |
Ответы |
Re: adding support for posix_fadvise()
Re: adding support for posix_fadvise() |
Список | pgsql-hackers |
On Mon, 2003-11-03 at 10:01, Tom Lane wrote: > Neil Conway <neilc@samurai.com> writes: > > POSIX_FADV_RANDOM doesn't effect the page cache, it just determines how > > aggressive the kernel is when doing readahead (at least on Linux, but > > I'd expect to see other kernels implement similar behavior). > > I would expect POSIX_FADV_SEQUENTIAL to reduce the chance that a page > will be kept in buffer cache after it's been used. I don't think that can be reasonably implied from the POSIX text, which is merely: POSIX_FADV_SEQUENTIAL Specifies that the application expects to access the specified data sequentially from loweroffsets to higher offsets. The present Linux implementation doesn't do this, AFAICS -- all it does it increase the readahead for this file: http://lxr.linux.no/source/mm/fadvise.c?v=2.6.0-test7 -Neil
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