| From: | Robert Lor <Robert(dot)Lor(at)Sun(dot)COM> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Fujii Masao <masao(dot)fujii(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, pgsql-hackers list <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: DTrace probes patch |
| Date: | 2008-12-17 19:49:12 |
| Message-ID: | 494957B8.8050009@sun.com |
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| Thread: | |
| Lists: | pgsql-hackers |
Alvaro Herrera wrote:
> But there are 5 callers of XLogWrite ... why aren't the other ones being
> tracked too?
>
>
This probe originally came from Simon, so it can't possibly be wrong :-)
My understanding is that we only want to track the XLogWrite when
advancing to the next buffer page, and if there is unwritten data in the
new buffer page, that indicates no more empty WAL buffer pages
available, but I may be wrong. I did some tests by adjusting
wal_buffers, and I could observe this behavior, more calls to XLogWrite
with smaller wal_buffers.
-Robert
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