| From: | Ben Chobot <bench(at)silentmedia(dot)com> |
|---|---|
| To: | Greg Smith <greg(at)2ndquadrant(dot)com> |
| Cc: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: tuning bgwriter in 8.4.2 |
| Date: | 2010-02-23 16:23:51 |
| Message-ID: | 42A2FC35-77D2-4C28-9435-FDE2C9AD0A43@silentmedia.com |
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| Thread: | |
| Lists: | pgsql-general |
On Feb 22, 2010, at 6:47 PM, Greg Smith wrote:
> Ben Chobot wrote:
>> Is it reading it correctly to say that the bgwriter probably wouldn't help much, because a majority of the dirty pages appear to be popular?
>
> Yes. The background writer cleaner process only does something useful if there are pages with low usage counts it can evict. You would need to increase shared_buffers significantly before it's likely that would happen. Right now, 87% of your buffer cache has a usage count of 2 or higher, which basically means it's filled with almost nothing but the working set of data it never wants to evict unless it's for a checkpoint.
Hm, my shared_buffers is already 10GB, but I'm using about 80GB for filesystem cache. Would a larger shared_buffers make sense? I thought I read somewhere that 10GB is on the high end of the useful size for shared_buffers.
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