Hi Timo et al,
On 29 Mar 2007, at 17:52, Mike Brudenell wrote:
But then the ODDNESS starts. I'm still a little hazy how to
interpret the output of imaptest, but every now and then one or two
processes stall for several seconds. When this happens activity
seems to grow quieter in the imaptest output: number of operations
per second decreases and the N/N count drops. Eventually it clears
somehow and things spring back into life...
Further to my message to the list yesterday I'm still baffled and
concerned as to why imaptest10 shows stalls in SELECT occasionally
and, when it does so, it looks like all other clients are blocked or
something.
When the Maildir mailstore is mounted over NFS from our NetApp filer
to the Solaris 10 box Dovecot and imaptest10 are running on the
problem shows.
Switch to using local disk for the mailstore and run imaptest10 with
the same number of clients and there are no stalls. But increase the
number of simulated clients (from 50 to 100) and they come back, but
not too badly at that setting.
So it looks like something to do with when the system gets really
loaded...
I think the things I'd like to know are:
Are other people on the List running Dovecot with Maildir mailstore NFS-mounted from NetApp filers and having it work OK? (If you are using Solaris 10, what mount options are you using?)
How much real-life user load does running imaptest10 with 50
simulated clients equate to? I assume each simulated user is hammering
away at its IMAP connection, so should equate to several (how many?) normal users in real-life operation?I'm concerned by the N/M number at the end of the imaptest10 output lines plummeting whenever one process goes into this stalled state: it almost suggests as if the only thing the other processes can
do is logout? Are other sessions really being blocked, or is it just imaptest10 behaving like this?As far as I can tell I *think* it's only imaptest10 getting
blocked: when it is happening for an extended period I can quickly manually Telnet in to port 143, login as one of the test usernames and
SELECT INBOX just fine. So it's probably NOT all of the Dovecot processes getting blocked, but imaptest10 that drives them. Does that sound plausible?
Help! (Concerned, and hoping we're not going down the wrong road...
can anyone reassure me about the Solaris 10/NFS/NetApp filer setup?)
With thanks, Mike B-)
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EXAMPLE OUTPUT FROM IMAPTEST10
24 13 20 28 25 36 10 14 23 24 48 50/ 50 32 15 15 28 28 46 18 16 35 32 64 50/ 50 21 13 14 27 30 32 9 8 21 22 42 50/ 50
- stalled for 16 secs in SELECT 0 5 2 6 7 27 10 18 26 28 58 21/ 21 <=== 46 22 25 40 38 38 8 12 21 17 34 50/ 50 28 11 13 24 22 32 9 6 24 28 56 50/ 50 20 10 15 24 27 38 13 10 24 20 40 50/ 50 29 9 11 25 21 33 13 14 28 29 58 50/ 50 28 17 12 32 37 43 17 15 27 28 56 50/ 50
and
34 15 13 28 27 47 16 20 34 34 68 50/ 50 18 13 16 27 25 23 9 13 17 18 36 50/ 50 21 9 8 22 25 36 17 13 23 22 42 50/ 50
- stalled for 16 secs in SELECT
- stalled for 16 secs in SELECT Logi List Stat Sele Fetc Fet2 Stor Dele Expu Appe Logo 100% 50% 50% 100% 100% 100% 50% 100% 100% 100% 100% 30% 5% 0 5 2 7 7 28 11 12 28 29 60 20/ 20 <=== 41 16 18 31 26 24 6 4 12 11 22 50/ 50 29 9 15 28 29 42 10 13 27 29 58 50/ 50