| From: | Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Page-at-a-time Locking Considerations |
| Date: | 2008-02-06 21:07:00 |
| Message-ID: | 47AA2174.3060409@sun.com |
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| Thread: | |
| Lists: | pgsql-hackers |
Tom Lane wrote:
> Zdenek Kotala <Zdenek(dot)Kotala(at)Sun(dot)COM> writes:
>> Tom Lane wrote:
>>> If you only got 2% out of it, it's not even worth thinking about how to
>>> fix the serious bugs that approach would create (primarily, lack of
>>> control over when pages can get flushed to disk).
>
>> You can flush a pages by msync() function which writes dirty pages on
>> disk. I don't see any other problem.
>
> Then you need to learn more. The side of the problem that is hard to
> fix is that sometimes we need to prevent pages from being flushed to
> disk until some other data (typically WAL entries) has reached disk.
> With mmap'd data we have no control over early writes.
I see. Thanks for explanation.
Zdenek
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