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Re: Load Distributed Checkpoints, take 3

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
Cc: Greg Smith <gsmith(at)gregsmith(dot)com>, Patches <pgsql-patches(at)postgresql(dot)org>
Subject: Re: Load Distributed Checkpoints, take 3
Date: 2007-06-25 17:13:46
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-patches
Heikki Linnakangas <heikki(at)enterprisedb(dot)com> writes:
> On further thought, there is one workload where removing the non-LRU 
> part would be counterproductive:

> If you have a system with a very bursty transaction rate, it's possible 
> that when it's time for a checkpoint, there hasn't been any WAL logged 
> activity since last checkpoint, so we skip it. When that happens, the 
> buffer cache might still be full of dirty pages, because of hint bit 
> updates. That still isn't a problem on it's own, but if you then do a 
> huge batch update, you have to flush those dirty pages at that point. It 
> would be better to trickle flush those dirty pages during the idle period.

But wouldn't the LRU-based scan accomplish that?

			regards, tom lane

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