PHP processes & children

Denis S. Filimonov den.lists at
Tue May 20 22:01:03 MSD 2008

From PHP performance perspective, one master with 32 children will do better 
because they will share more memory pages and have slightly smaller memory 
footprint. Besides, the master process doesn't do anything other than 
re-spawning dead children, which is a rare event.

There is one case when you might want multiple master processes, though.
If your server handles multiple sites with different databases, you may want 
to separate them on one php pool per database basis. The reason is that in 
databases queries can stall until another query terminates (particularly in 
MySQL with MyISAM tables). So, if the query takes significant time compared 
to the request rate, the whole php pool will get stuck waiting for the 
database. If your other sites are handled by other php pools they'll have 
little to no impact, otherwise they'll stall as well.

On Tuesday 20 May 2008 10:28:01 Igor Clark wrote:
> Hi there
> Not strictly an nginx question but don't know where else to ask and I
> think some of you will have valuable opinions on this!
> nginx <-- fastcgi --> php
> Is it better to have 1 PHP master process on 1 port re-spawning many
> children, or many PHP masters on many ports spawning fewer children?
> E.g.  one master with e.g. 32 worker children on 1 port, or 4 masters
> with 8 children each on 4 ports?
> Initial thoughts would be more masters as it's a multi-core box, but
> not sure, if all cores are switching and respawning could that get
> expensive?
> Many thanks for any input ...
> Igor
> --
> Igor Clark • POKE • 10 Redchurch Street • E2 7DD • +44 (0)20 7749 5355
> •


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