[Dovecot] 2.0, hourly performance stats

[Timo Sirainen]

On Mon, 2010-11-08 at 08:34 +0100, Ralf Hildebrandt wrote: 
> I'm getting constantly high numbers of page reclaims & involuntary
> context switches for dovecot/auth.
> 
> page reclaims = minor faults = cpu switching back to system-mode, But
> why is the auth process doing that so excessively? Same for the large
> number of involuntary context switches...

Hmm. "A page reclaim occurs when a requested page exists on the free
list. A page reclaim results in a page fault being satisfied in
memory." 
> Date: Mon, 08 Nov 2010 01:00:01 +0100
> 
> type	        real	user	sys	reclaim	faults	swaps	bin	bout	signals	volcs	involcs
> auth	        421.98	1.32	1.66	24216	0	0	0	0	0	267	723
> managesieve-lo	18616.9	86.77	32.49	319768	1	0	168	0	0	63448	48838

The managesieve-login is pretty high here too. Much worse than auth
process. Were there tons of logins at that time? Or some brute force
password guessing, or some other DoSing? Perhaps the problem is actually
managesieve-login alone? Did you set also service managesieve-login
{ service_count=0 } ?

I'm currently seeing in my test machine where imaptest is runnng
something like:

type	real	user	sys	recla	faults	swaps	bin	bout	signals	volcs	involcs
master	1252.14	0.58	2.70	138271	0	0	0	16	0	30101	69
anvil	1252.13	0.27	0.23	336	0	0	0	0	0	16739	6
imap	2.34	0.11	0.20	1548	0	0	0	856	0	22	144
imap-lo	0.11	0.00	0.80	622	0	0	0	0	0	6	19
auth	1248.45	1.26	0.91	841	16	0	3248	0	0	51559	118
log	1252.84	0.86	1.12	347	0	0	8	4560	0	47245	27
config	1252.12	13.57	0.59	1061	0	0	0	0	0	36574	727
lmtp	41.43	0.40	0.80	495	11	0	2328	0	0	25	14

The config process's high user CPU% is expected. Master is doing a lot
of page reclaims, which I'd guess is because it's forking a lot.