Tickets :: Comment on [#13747] Speed up ActiveSync synchronisation handling

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Comment	>> Dear Horde team, >> I have noticed some performance issues in Horde with email "power users".. >> >> "Power users" are users having > than 150 message folders and 25k >> messages in them.. (just to have an idea about what I'm speaking) >> >> Every time a power user logs in via ActiveSync (Outlook 2013, ..) the > > I would fall into this category, though not ALL of my folders have > that many messages. I don't see such a slowdown, but I do not use > Apache. > >> apache service rises up to 100% CPU usage for 3-6 seconds. >> Also, every time a power user mark just 1 message as read/unread the >> same problem arise. > >> The bottleneck seems to be just the Horde service (apache). >> There is practically no access to harddisks and/or other hardware >> during the CPU usage spike. > > FIrst, I am going to assume you are using an efficient IMAP server > such as Dovecot that supports, among other things, modification > sequences. Otherwise, your performance for such a large mailbox will > degrade. > > The way the mail synchronization works for such an IMAP server (and > I'm heavily simplifying) is that we remember the last MODSEQ of each > mailbox and then basically perform a time-escaped loop that queries > the IMAP server for changes in each folder since that folder's > MODSEQ. After each folder is queried (assuming no changes were > found) we sleep a configurable number of seconds and then repeat the > process. The loop (and eventually the request) exit either when a > change is found, or the heartbeat interval is reached. There is no > "looping over every message in the folder" as you had asked in the > mailing list. Checking each folder for changes (should be) a very > fast operation - limited by your IMAP server's performance. For large > number of folders, each loop iteration might take some time, but > there is nothing we can about that since it is the only way to detect > changes. A unique-ish thing about OL is that it ALWAYS polls ALL > folders. It's not configurable like just about every other EAS client > out there. > > On the Horde side, the only thing I can think of for such a large > number of messages is that it might be related to the state storage > since even for MODSEQ servers, we need to cache a (compressed) list > of message uids that are on the device. > >> Is there any possibility to investigate further? > > You should investigate using a tool such as xdebug to profile where > this time is being spent. > >> Could there be some needless loops in Horde that could be optimized? > > Anything is possible. Again, xdebug will be your friend here.
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