Load spikes when new email arrives

[Jean Raby]

On 13-01-23 11:16 AM, francis picabia wrote:
>
> Here are more stats.  Do these look average for performance?
> It is difficult to understand why the system was working with few
> load spikes before.
>
> A mailman mailing list sends 10kbyte message to 4000
> users having accounts on this cyrus system.  If I
> grep "Delivered" in the maillog by the minute I can
> see how fast the messages are stored.
What backend are you using for the duplicate_db (deliver.db)?

I've seen much better delivery performance using berkeley-nosync instead 
of the default (skiplist) for this one.

>
> e.g.:
> # grep Delivered /var/log/maillog | grep 'Jan 23 10:37' | wc -l
>      696
>
> That is the best.  This peak event pushed the load to 14
> for 12 minutes, where it averages 604 messages
> delivered to cyrus mailboxes per minute.  Is that
> reasonable for  maximum delivery rate?
>
> I've also backed out the change (yesterday) to
> /sys/block/sda/queue/nr_requests
> I think it was pushing the load higher and there is no advantage
> in my hardware (SAS with Perc 5/i Raid 5 over 4 disk)
> to run with a low value for nr_requests.
>
>
>
>
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Jean Raby
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