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Subject: Re: [OMPI devel] kernel 2.6.23 vs 2.6.24 - communication/wait times
From: Ashley Pittman (ashley_at_[hidden])
Date: 2010-04-10 15:20:52


On 10 Apr 2010, at 04:51, Eugene Loh wrote:

> Why is shared-memory performance about four orders of magnitude slower than it should be? The processes are communicating via memory that's shared by having the processes all mmap the same file into their address spaces. Is it possible that with the newer kernels, operations to that shared file are going all the way out to disk? Maybe you don't know the answer, but hopefully someone on this mail list can provide some insight.

Is the /tmp filesystem on NFS by any chance?

Ashley,

-- 
Ashley Pittman, Bath, UK.
Padb - A parallel job inspection tool for cluster computing
http://padb.pittman.org.uk