Re: process creation time increases linearly with shmem

From: Nick Piggin
Date: Mon Aug 29 2005 - 19:52:38 EST


Ray Fucillo wrote:

Nick Piggin wrote:

How does the following look? (I changed the comment a bit). Andrew, please
apply if nobody objects.


Nick, I applied this latest patch to a 2.6.12 kernel and found that it does resolve the problem. Prior to the patch on this machine, I was seeing about 23ms spent in fork for ever 100MB of shared memory segment. After applying the patch, fork is taking about 1ms regardless of the shared memory size.


Hi Ray,
That's good news. I think we should probably consider putting the patch in
2.6.14 or if not, then definitely 2.6.15.

Andrew, did you pick up the patch or should I resend to someone?

I think the fork latency alone is enough to justify inclusion... however, did
you actually see increased aggregate throughput of your database (or at least
not a _decreased_ throughput)?

Many thanks to everyone for your help on this.


Well thank you very much for breaking the kernel and telling us about it! :)

Nick


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