From: | Scott Mead <scott(dot)lists(at)enterprisedb(dot)com> |
---|---|
To: | Greg Smith <gsmith(at)gregsmith(dot)com> |
Cc: | Brian Troutwine <goofyheadedpunk(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: Terrible Write Performance of a Stored Procedure |
Date: | 2009-06-29 12:54:40 |
Message-ID: | d3ab2ec80906290554j564dcdew7f992407df34882e@mail.gmail.com |
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Lists: | pgsql-general pgsql-performance |
>
> You're right that it should be removed, but this explanation is wrong. The
> behavior as configured is actually "if there are >=100 other transactions in
> progress, wait 0.1 second before committing after the first one gets
> committed", in hopes that one of the other 100 might also join along in the
> disk write.
Thanks for the correction. My question is how you're getting .1 seconds
from his commit_delay?
if (CommitDelay > 0 && enableFsync &&
CountActiveBackends() >= CommitSiblings)
pg_usleep(CommitDelay);
Wouldn't this actually be 1 second based on a commit_delay of 100000?
>
>
> Since in this case max_connections it set to 100, it's actually impossible
> for the commit_delay/commit_siblings behavior to trigger give this
> configuration. That's one reason it should be removed. The other is that i
> general, if you don't exactly what you're doing, you shouldn't be touching
> either parameters; they don't do what people expect them to and it's
> extremely unlikely you'll encounter any of the rare use cases where they
> might help.
After looking, I agree, thanks again for the correction Greg.
--Scott
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