| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Jan Wieck <JanWieck(at)Yahoo(dot)com> |
| Cc: | pgsql-hackers(at)postgreSQL(dot)org |
| Subject: | Re: Why are these ARC variables per-backend? |
| Date: | 2004-04-19 19:21:35 |
| Message-ID: | 27747.1082402495@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Jan Wieck <JanWieck(at)Yahoo(dot)com> writes:
> Tom Lane wrote:
>> Why do we have it at all? Seems like it would be at least as good to
>> make the T1-or-T2 decision in StrategyGetBuffer, rather than earlier.
> If it'd be possible. The problem is that it can get called multiple
> times during one logical buffer lookup/fault cycle. Because of the
> possible IO, which is done in the caller of the strategy, this would
> screw up the decision process about the queue sizes.
How so? It seems like postponing the decision about which queue to take
from couldn't make the behavior worse; if anything it would help to
track T1target more closely.
regards, tom lane
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