What application that suit with MongoDB.

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Nites Bootkhot

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Jun 6, 2012, 9:50:59 AM6/6/12
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MognoDB has global write lock.
So it suit with application which rarely write and often read.
Is that right?

Thanks.

John Wood (maverin)

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Jun 6, 2012, 10:46:22 AM6/6/12
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My understanding is that the global write lock is for a very short memory write, and if it has to write to disk it relinquishes the lock until the paging operation is complete... so it's not as bad as it sounds. 

Nites Bootkhot

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Jun 6, 2012, 11:11:12 AM6/6/12
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Yes, thanks John.
I'm looking forward to document-level locking.
Good job for developer team.
Cheer! 
--
Nites Bootkhot
Software Engineer
Intelligent Millionaire



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Scott Hernandez

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Jun 6, 2012, 11:22:20 AM6/6/12
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Yes, that is correct. If disk access will be done in the (write) lock
then the lock is released until after the disk access. In 2.0.x this
happened in a good number of places and in 2.2.x it will happen almost
everywhere (we have a new exception system to generalize this
behavior).

This leads to very high concurrency even with just the greedy writer
(reader/writer) lock since it is just cpu/memory bound.

More granular locks will be good, but these yields on long running,
slow or disk operations already provide good performance.
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