On Aug 8, 2006, at 5:43 PM, James Berry wrote:
Hi Timo, (By the way, this seems to relate to a performance issue
on Mac OS X with HFS+).
I think the problem may be more general than this particular case.
This fix speeds up some accesses, but there are still bottlenecks, I
believe. I have a feeling the performance issues will manifest in any
cases where hardlinks are used heavily.
Can you tell me, Timo, in what other cases hard links are used (file
copy, seemingly being one) and whether there is any way to turn them
off or rework the code to avoid them?
Thanks!
James
On Aug 28, 2005, at 12:30 PM, Timo Sirainen wrote:
On Thu, 2005-08-25 at 10:26 -0700, James Berry wrote:
If I read the code correctly, only dotlocks are supported for
locking of dovecot-uidlist. And I don't see any settings in the config file for it.As it turns out, dotlocks are very slow on my system, due to their implementation via hardlinks.
Would it be possible to support other locking mechanisms for locking of the uidlist file?
They are locked only when they are modified, and the modification
works by creating a new file and renaming it over the dovecot-uidlist file.Is it only hardlinks that are problematic? It shouldn't be too
difficult to change the dotlock code to rely on working O_EXCL instead of hardlinks.Hmm. Actually I just did that in CVS. I guess I should also put
out some setting to enable it in config file. For now you could just change
this:ret = set->use_excl_lock ? try_create_lock_excl(&lock_info, write_pid) : try_create_lock_hardlink(&lock_info, write_pid);
to
ret = try_create_lock_excl(&lock_info, write_pid);
and see if it works faster.
Well, a year later I finally got around to trying this out. On a
Mac system. And guess what? It seems much, much snappier. Sorry
about the delay in testing it. One of the symptoms I've been seeing
on the server is that performance gradually degrades over time,
even if dovecot is restarted. The problem seems better after a
server restart, which clears out an area on disk which tracks
unlinked and hardlinked files. I believe this option will fix that
performance issue.Any chance of getting a configuration option for this?
James