Re: Large tables (was: RAID 0 not as fast as

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От Ron Mayer
Тема Re: Large tables (was: RAID 0 not as fast as
Дата
Msg-id 4516884E.6070308@cheapcomplexdevices.com
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Ответ на Re: Large tables (was: RAID 0 not as fast as  ("Luke Lonergan" <llonergan@greenplum.com>)
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Luke Lonergan wrote:
>
> I think the topic is similar to "cache bypass", used in cache capable vector
> processors (Cray, Convex, Multiflow, etc) in the 90's.  When you are
> scanning through something larger than the cache, it should be marked
> "non-cacheable" and bypass caching altogether.  This avoids a copy, and
> keeps the cache available for things that can benefit from it.

And 'course some file systems do this automatically when they
detect a sequential scan[1] though it can have unexpected (to some)
negative side effects[2].   For file systems that support freebehind
as a configurable parameter, it might be easier to experiment with
the idea there.

[1]
http://www.ediaudit.com/doc_sol10/Solaris_10_Doc/common/SUNWaadm/reloc/sun_docs/C/solaris_10/SUNWaadm/SOLTUNEPARAMREF/p18.html
[2] http://bugs.opensolaris.org/bugdatabase/view_bug.do?bug_id=6207772



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