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Re: Performance degredation between 2.4.39 and 2.4.44

--On Tuesday, March 15, 2016 1:31 PM +0000 Howard Chu <hyc@symas.com> wrote:

I see the differences I've noted with at least 3 different DBs of
varying size now. I've dropped the 300kish one on ada.

With your 300k entry DB and config I see a full subtree search take about
10.4s with rtxnsize = 0, vs 11.7s with rtxnsize = 10000. Measurable
certainly, but not really noticeable.

As I noted, a 30:1 ratio seems to work ok. Now, if you go back to my original mail, the problem is the default of 10k is clearly not sufficient for any medium+ sized db. I think a mistake was made in setting the default in 2.4.44 to anything other than zero. This is clearly an item that needs tuning PER database, and should not have a default that creates a severe performance penalty on databases > 300000 entries. As you can see from my other emails, the further you get from the 30:1 ratio, the more significant the penalty in performance. It would be interesting to know if there are further ways to optimize the code so that the penalty is not so severe. I.e., the next step would be to set the rtxnsize to 1000 with the 300k database and see if there are further optimizations to be had.



Quanah Gibson-Mount
Platform Architect
Zimbra, Inc.
Zimbra ::  the leader in open source messaging and collaboration
A division of Synacor, Inc