[SR-Users] suggested number of TCP / UDP workers for version 3.1.x

[Daniel-Constantin Mierla]

Hello,

On 8/3/11 6:28 PM, Francesco Castellano wrote:
> Dear sirs,
>
> searching on the web and in old ML threads about the suggested number
> of TCP and UDP workers, I just found:
>
> - for TCP children (i.e., TCP receivers, isn't it?)
> "As a rule of thumb, (maximum simultaneous connections)/2000 should be
> OK" (from doc/tcp_tunning.txt)
>
> - In general for workers (from a past thread by Henning Westerholt):
> "In my experience the number of children is not that important for
> performance, you may just choose the default size of 8."
>
> In the last post there was, moreover, a suggestion that the number of
> children should be chosen with respect to RAM and CPU cores (that
> makes sense to me).
>
> The only thing I can think about the rule of thumb above comes from
> the possibility that a number of processes may be unavailable in
> blocking operations. So my question is:
>
> - with asynchronous TCP/TLS is it safe to assume that more children
> than CPU cores are more or less useless?
No, unless you have a lot of cores. There is a lot of I/O with the 
networking, database a.s.o. The number of children is a matter of 
traffic and the time consuming operations you do (db lookups, dns).

> - are there other blocking operations for which the number of UDP/TCP
> children should be incremented above the CPU cores number?

No matter the number of cores, in production I start from 8 children and 
don't go more than 32. After this value, either the config is too 
blocking or the traffic is too high and it is time for new hardware. I 
am talking about usual server hardware, not supercomputers.

Cheers,
Daniel

-- 
Daniel-Constantin Mierla -- http://www.asipto.com
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