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List:       openldap-devel
Subject:    Re: better malloc strategies
From:       Howard Chu <hyc () symas ! com>
Date:       2006-11-23 3:00:59
Message-ID: 45650EEB.3000606 () symas ! com
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David Boreham wrote:
> Howard Chu wrote:
> 
>> What's also interesting is that for Hoard, Umem, and Tcmalloc, the 
>> multi-threaded query times are consistently about 2x slower than the 
>> single-threaded case. The 2x slowdown makes sense since it's only a 
>> dual-core CPU and it's doing 4x as much work. This kinda says that the 
>> cost of malloc is overshadowed by the overhead of thread scheduling.
> 
> Is it possible that the block stride in the addresses returned by 
> malloc() is affecting
> cache performance in the glibc case ?
> If they are too close I think it is possible to thrash cache lines 
> between cores.

That's a very good question, and I don't have an answer yet. I've been 
working on some threading extensions for cachegrind so I can investigate 
that. Unfortunately its existing infrastructure doesn't lend itself well 
to tracking multiple caches, so that's been slow going.

-- 
   -- Howard Chu
   Chief Architect, Symas Corp.  http://www.symas.com
   Director, Highland Sun        http://highlandsun.com/hyc
   OpenLDAP Core Team            http://www.openldap.org/project/
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