[ZODB-Dev] Re: [Enhancement Proposal] Memory size limited Cache

[Jim Fulton]

Tres Seaver wrote:
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> Jim Fulton wrote:
>> Dieter Maurer wrote:
>>> Jim Fulton wrote at 2006-10-6 12:21 -0400:
>>>> ...
>>>>> We would have a use case for this, too.
>>>> We've started moving toward just using a single application thread
>>>> per process
>>>> (with many processes).  There isn't really much advantage in running
>>>> multiple
>>>> threads if you have multiple processes. 
>>> Apart from sharing resources, such as the cache....
>> That isn't a benefit of multiple threads.  It is a way to
>> mitigate the cost of multiple threads.  In the presence of the
>> GIL there is no throughput benefit in running multiple threads.
>> The only benefit of multiple threads is that it is somewhat
>> less likely that expensive requests will block inexpensive ones.
> 
> Assuming that you aren't disk or RAM constrained, I'll agree that
> running multiple processes is more likely to win, especially on
> multi-CPU machines.  However, most sites which have such needs might do
> better to have a single, *large* cache, than many smaller ones;
> swapping will kill any benefit obtained from better parallelism.

Sure.  I would definitely not run more processes than processors
(assuming that the processes are identical).  And I wouldn't
use more than one thread unless responsiveness was an issue, as
it sometimes is.

Jim

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