> Ideally, autovacuum would only request a new copy of the file if the
> one it got was considerably out of date. Obviously a tenth of a
> second is not old enough.
I've tried to look at it and found that's already implemented - see
autovac_refresh_stats(). STATS_READ_DELAY which is set to 1s. Am I
reading the code correctly? If so then 1s is not enough for big clusters.
I guess it would be feasible to crank STATS_READ_DELAY up a little bit,
say to 10s. What do you think?
Kuba
Dne 16.2.2010 19:59, Alvaro Herrera napsal(a):
Jakub Ouhrabka wrote:
Maybe you should decrease naptime a bit.
That did the trick, thanks!
Yes. There were some changes that needed to be done to autovacuum so
that it didn't read the stats file too often, but I don't recall if I
got around to it.
I looked at the strace output and there are *writes* to the file not
reads. Why? Is it a consequence of this optimization?
Release notes 8.4:
Reduce I/O load of writing the statistics collection file by writing
the file only when requested (Martin Pihlak)
Was autovacuum requesting to write this 20MB file 650x per minute?
Yes, exactly.
Ideally, autovacuum would only request a new copy of the file if the one
it got was considerably out of date. Obviously a tenth of a second is
not old enough.
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