AOF_FSYNC_EVERYSEC higher resolution, change aof_last_fsync and...
AOF_FSYNC_EVERYSEC higher resolution, change aof_last_fsync and aof_flush_postponed_start to use mstime (#13041)
Currently aof_last_fsync is using a low resolution unixtime is really
bad,
it checks if the absolute number of (full) seconds changed by one.
depending on which side of the second barrier it falls, we can get very
different results.
This PR change the resolution to use milliseconds instead of complete
seconds.
In cases where the event loop cycle duration is short and their rapid
(e.g. running
many fast commands with short pipeline, or a high `hz` config), this
change will not
make much difference, since in anyway, we'll be quick to detect that
we're on a "new
second", and it's likely that these fsync will always be executed close
to the second
switch barrier.
But in cases of rare or slow event loops cycles (e.g. either slow
commands, or very
low rate of traffic to redis, and low `hz`), it could easily be that
with the old code,
in some cases we'll have over 1.5 seconds between fsyncs, and in others
less than 0.5.
see discussion in #8612
This PR also handle aof_flush_postponed_start as well, the damage there
is smaller
since the threshold is 2 seconds, and not 1.
---------
Co-authored-by:
Oran Agra <oran@redislabs.com>
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