On 2013-12-05 11:15:20 +0200, Metin Doslu wrote:
> > - When we increased NUM_BUFFER_PARTITIONS to 1024, this problem is
> > disappeared for 8 core machines and come back with 16 core machines on
> > Amazon EC2. Would it be related with PostgreSQL locking mechanism?
> If we build with -DLWLOCK_STATS to print locking stats from PostgreSQL, we
> see tons of contention with default value of NUM_BUFFER_PARTITIONS which is
> 16:

Is your workload bigger than RAM? I think a good bit of the contention
you're seeing in that listing is populating shared_buffers - and might
actually vanish once you're halfway cached.
>From what I've seen so far the bigger problem than contention in the
lwlocks itself, is the spinlock protecting the lwlocks...


Andres Freund

 Andres Freund                     http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

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