[Dovecot] strange email client problems

[Jens Laas]

(05.03.21 kl.15:03) Gabriel Granger skrev följande till Timo Sirainen:

> I will set that option tonight and see how what happens when my users login 
> tomorrow morning.  With regards to the load of the server its about 0.03 at 
> present and when a user complained about "Loading messages" about 30mins ago, 
> I checked the server and it was abut the same.  I'm really not sure how to 
> see the load of the HD's from the console or even what I could compare it 
> against.
>
> Mem:   1035180k total,  1014672k used,    20508k free,    33556k buffers
> Swap:  1052216k total,        0k used,  1052216k free,   920644k cached
>
> I  notice the server is using a lot of real memory but with loads of swap 
> available for use if thats of any use.  When I used to use UW-IMAP i used to 
> get a lot more CPU load which has since disappear now that I'm using Dovecot.

The use of real memory is no good indicator since the OS will use as much 
as possible for buffers.
If the system starts using swap in a big way then this is a good 
indication that you are running out of memory or I/O.

To see a general system load (in Linux) use vmstat.
root# vmstat 5 10|cut -c 8-
----------memory---------- ---swap-- -----io---- --system-- ----cpu----
  swpd   free   buff  cache   si   so    bi    bo   in    cs us sy id wa
    12  57104  50004 1813592    0    0     1     0    1     1  3  1 93  4
    12  16288  50064 1855692    0    0  8429   536 1439  1252  3  1 88  8
    12  39288  50100 1833692    0    0  5026   973 1375  1048  4  2 88  7
    12  13332  49700 1858300    0    0 17262   905 1762   889 17  2 71 10
    12  90096  49860 1781368    0    0 35019  1434 1801  1791 13  3 60 24

Of special interest is si, so, bi, bo, wa.
        so: Amount of memory swapped to disk (/s).
        wa: Time spent waiting for IO.
(There are other info to get via vmstat too. Use man :)

Cheers,
Jens

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     Jens Låås                              Email: jens.laas at data.slu.se
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