| From: | Florian Weimer <fw(at)deneb(dot)enyo(dot)de> | 
|---|---|
| To: | "Jim C(dot) Nasby" <jnasby(at)pervasive(dot)com> | 
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org | 
| Subject: | Re: Compression and on-disk sorting | 
| Date: | 2006-05-18 05:36:11 | 
| Message-ID: | 87ac9fuc6s.fsf@mid.deneb.enyo.de | 
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| Lists: | pgsql-hackers | 
* Jim C. Nasby:
> The problem is that it seems like there's never enough ability to clue
> the OS in on what the application is trying to accomplish. For a long
> time we didn't have a background writer, because the OS should be able
> to flush things out on it's own before checkpoint. Now there's talk of a
> background reader, because backends keep stalling on waiting on disk IO.
I've recently seen this on one of our test systems -- neither CPU nor
disk I/O were maxed out.
Have you considered using asynchronous I/O?  Maybe it results in less
complexity and fewer context switches than a background reader.
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