Re: concurrent IO in postgres?

On 12/25/10, Mladen Gogala <mladen.gogala@vmsinfo.com> wrote:
> Jeff Janes wrote:
>> If the background writer cannot keep up, then the individual backends
>> start doing writes as well, so it isn't really serialized..
>>
>>
> Is there any parameter governing that behavior?

No, it is automatic.

There are parameters governing how likely it is that bgwriter falls
behind in the first place, though.

http://www.postgresql.org/docs/9.0/static/runtime-config-resource.html

In particular bgwriter_lru_maxpages could be made bigger and/or
bgwriter_delay smaller.

But bulk copy binary might use a nondefault allocation strategy, and I
don't know enough about that part of the code to assess the
interaction of that with bgwriter.

> Can you tell me where in
> the code (version 9.0.2) can I find
that? Thanks.

Bufmgr.c, specifically BufferAlloc.

Cheers,

Jeff