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From Chris Anderson <jch...@apache.org>
Subject Re: couchdb on smp?
Date Mon, 04 May 2009 15:58:57 GMT
On Mon, May 4, 2009 at 7:23 AM, Zachary Zolton <zachary.zolton@gmail.com> wrote:
> @janl
>
> Perhaps he's asking why there's no activity on the other processor?
>
> I think his expectation here is that Map-Reduce would be parallelized.
> Correct me if I'm wrong, but CouchDB does not yet exploit parallelism
> in view indexing yet, right?
>

Correct. And the JavaScript view server doesn't make it easy to do so
without starting multiple OS processes per map-function. I can see
this being nifty down the road, but it's an optimization.

However, interest is growing in an Erlang view server, and
http://github.com/mmcdanie/erlview points out that the view process
architecture could use some changes to make Erlang views parallel.
Those changes will in turn make it more trivial to parallelize JS view
computation, in the cases that need it. So I can see us getting to
parallel JS views, but I think the cleaner way to get there is to
start with proper Erlang views.

> —zdzolton
>
> On Mon, May 4, 2009 at 7:46 AM, Jan Lehnardt <jan@apache.org> wrote:
>> Beam and couchjs pipe data back and  forth during view generation. While the
>> one works, the other waits. The scheduler is smart enough to keep the
>> processes local to a single CPU. Otherwise it's be even more expensive.
>>
>> Cheers
>> Jan
>> --
>>
>> On 04.05.2009, at 12:50, Elf <elf2001@gmail.com> wrote:
>>
>>> Hello.
>>> I'm using couchdb-0.9 (erlang 13.2) on my linux server with 4 CPUs
>>> (Core 2 Quad).
>>> Every time couchdb needs to reindex views, i see 2 serious processes
>>> in htop - beam and couchjs. Each of them eats < 100% of 1 cpu, and sum
>>> of their usage is about (but not greater) 100% of 1 cpu (80/20, 70/30
>>> and so on).
>>> Can somebody explain, why that 2 different processes (they have
>>> differend PIDs) doesn't used different cpus - (one process for cpu)?
>>>
>>>
>>> --
>>> ----------------
>>> Best regards
>>> Elf
>>> mailto:elf2001@gmail.com
>>>
>>
>



-- 
Chris Anderson
http://jchrisa.net
http://couch.io

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