| 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: | 1051.1182791626@sss.pgh.pa.us |
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| 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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