| From: | Michael Paquier <michael(at)paquier(dot)xyz> |
|---|---|
| To: | Antonin Houska <ah(at)cybertec(dot)at> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: MarkBufferDirtyHint() and LSN update |
| Date: | 2019-11-13 12:17:03 |
| Message-ID: | 20191113121703.GY1549@paquier.xyz |
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| Lists: | pgsql-hackers |
On Mon, Nov 11, 2019 at 10:03:14AM +0100, Antonin Houska wrote:
> This looks good to me.
Actually, no, this is not good. I have been studying more the patch,
and after stressing more this code path with a cluster having
checksums enabled and shared_buffers at 1MB, I have been able to make
a couple of page's LSNs go backwards with pgbench -s 100. The cause
was simply that the page got flushed with a newer LSN than what was
returned by XLogSaveBufferForHint() before taking the buffer header
lock, so updating only the LSN for a non-dirty page was simply
guarding against that.
--
Michael
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