Re: O_DIRECT option used?

Read the developer's FAQ on advanced features. We don't think it will
be a big win.

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Ruslan A Dautkhanov wrote:
> Hello,
>
> In the FreeBSD 4.5 appear additional O_DIRECT option for open(2),
> which mean "eliminate or reduce cache effects". I think, that double
> buffering the same disk blocks is ineffective. I grepped all
> PostgreSQL sources for this options and didn't find this anywhere.
> PgSQL have it's own disk caches, which should be smart
> (DB can know what data should be cached first better than OS).
> Why wasting OS memory for double caches? OS can use this caches
> for other disk blocks, so total cached disk blocks in whole
> system will be much bigger. If you have no plans to implement this,
> please let us know what source files I should looking for patching.
> I think it's somewhere DB tables files are opened (and maybe
> WAL files too). Thanks a lot on any comments.
>
>
>
> ---
> best regards,
> Ruslan A Dautkhanov rusland(at)scn(dot)ru

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