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Re: Bgwriter LRU cleaning: we've been going at this all wrong

From: Jim Nasby <decibel(at)decibel(dot)org>
To: Greg Smith <gsmith(at)gregsmith(dot)com>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Bgwriter LRU cleaning: we've been going at this all wrong
Date: 2007-06-29 13:13:11
Message-ID: 3852A1F4-459A-4FAF-8897-400EF02692D1@decibel.org (view raw or flat)
Thread:
Lists: pgsql-hackers
On Jun 28, 2007, at 7:55 AM, Greg Smith wrote:
> On Thu, 28 Jun 2007, ITAGAKI Takahiro wrote:
>> Do you need to increase shared_buffers in such case?
>
> If you have something going wild creating dirty buffers with a high  
> usage count faster than they are being written to disk, increasing  
> the size of the shared_buffers cache can just make the problem  
> worse--now you have an ever bigger pile of dirty mess to shovel at  
> checkpoint time.  The existing background writers are particularly  
> unsuited to helping out in this situation, I think the new planned  
> implementation will be much better.

Is this still a serious issue with LDC? I share Greg Stark's concern  
that we're going to end up wasting a lot of writes.

Perhaps part of the problem is that we're using a single count to  
track buffer usage; perhaps we need separate counts for reads vs writes?
--
Jim Nasby                                            jim(at)nasby(dot)net
EnterpriseDB      http://enterprisedb.com      512.569.9461 (cell)



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