Re: pg_test_fsync performance - Mailing list pgsql-hackers

From Tom Lane
Subject Re: pg_test_fsync performance
Date
Msg-id 24874.1329182883@sss.pgh.pa.us
Whole thread Raw
In response to Re: pg_test_fsync performance  (Robert Haas <robertmhaas@gmail.com>)
Responses Re: pg_test_fsync performance  (Bruce Momjian <bruce@momjian.us>)
List pgsql-hackers
Robert Haas <robertmhaas@gmail.com> writes:
> Instead of or in addition to a fixed number operations per test, maybe
> we should cut off each test after a certain amount of wall-clock time,
> like 15 seconds.

+1, I was about to suggest the same thing.  Running any of these tests
for a fixed number of iterations will result in drastic degradation of
accuracy as soon as the machine's behavior changes noticeably from what
you were expecting.  Run them for a fixed time period instead.  Or maybe
do a few, then check elapsed time and estimate a number of iterations to
use, if you're worried about the cost of doing gettimeofday after each
write.
        regards, tom lane


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