Will MongoDB use multiCore CPU?

[Peng Guo]

When MongoDB doing parallel query， will it use  multiCore CPU?

Thanks.

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Regards
    Peng Guo

[Andreas Jung]

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Peng Guo wrote:
> When MongoDB doing parallel query， will it use multiCore CPU?

What do you mean with parallel query? A single query won't be executed
in parallel but running several queries in parallel will use multiple
cpus. Limitation: map-reduce will not run in parallel.

- -aj
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[Dwight Merriman]

correct.

in a future version a single map/reduce will saturate all cores, this
is planned but not scheduled for a specific release (not imminent, not
1.8)

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[Peng Guo]

How about multiple db.eval()?

I will remove the lock in eval for not block the whole system.

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Regards
    Peng Guo

[Andreas Jung]

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Peng Guo wrote:
> How about multiple db.eval()?
>
> I will remove the lock in eval for not block the whole system.

Also without knowing the internals: also serialized - unless
there is strong build-in parallel support inside the MongoDB backend
(which is not yet the case afaik (likely the same issue as with map-reduce).

- -aj
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[Eliot Horowitz]

db.eval is also single thread like map/reduce.

The general problem being poor support for concurrency in javascript engines.

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[Markus Gattol]

Peng> When MongoDB doing parallel query， will it use multiCore CPU?
Peng> Thanks.

I think it is better to think in terms of "read operations" and "write
operations". With "read operations" we then split again in server-side
(JavaScript, run on the server) and client side (all various drivers
e.g. PyMongo). I have pimped my FAQs a bit to better reflect the
distinction:

http://www.markus-gattol.name/ws/mongodb.html#does_mongodb_use_more_than_one_cpu_core

[Peng Guo]

Thanks for you help :)

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Regards
    Peng Guo