| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Greg Smith <gsmith(at)gregsmith(dot)com> |
| Cc: | Dan Sugalski <dan(at)sidhe(dot)org>, pgsql-performance(at)postgresql(dot)org |
| Subject: | Re: PG 8.3 and large shared buffer settings |
| Date: | 2009-09-26 19:16:52 |
| Message-ID: | f67928030909261216r4e3a1ad7r5821f02f583c3206@mail.gmail.com |
| Views: | Raw Message | Whole Thread | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-performance |
On Sat, Sep 26, 2009 at 8:19 AM, Greg Smith <gsmith(at)gregsmith(dot)com> wrote:
>
> Another problem spot are checkpoints. If you dirty a very large buffer
> cache, that whole thing will have to get dumped to disk eventually, and on
> some workloads people have found they have to reduce shared_buffers
> specifically to keep this from being too painful.
Hi Greg,
Is this the case even if checkpoint_completion_target is set close to 1.0?
If you dirty buffers fast enough to dirty most of a huge
shared_buffers area between checkpoints, then it seems like lowering
the shared_buffers wouldn't reduce the amount of I/O needed, it would
just shift the I/O from checkpoints to the backends themselves.
It looks like checkpoint_completion_target was introduced in 8.3.0
Cheers,
Jeff
| From | Date | Subject | |
|---|---|---|---|
| Next Message | Greg Smith | 2009-09-26 21:19:11 | Re: PG 8.3 and large shared buffer settings |
| Previous Message | Jeff Janes | 2009-09-26 18:59:43 | Re: PG 8.3 and large shared buffer settings |