Chiheng Xu wrote:
---------- Forwarded message ----------
From: Chiheng Xu<[email protected]>
Date: Fri, Jul 30, 2010 at 6:02 PM
Subject: Re: [RFC]serialize the output of parallel make?
To: Tim Murphy<[email protected]>
On Fri, Jul 30, 2010 at 5:54 PM, Tim Murphy<[email protected]> wrote:
Hi,
The cost to the system of even starting a shell to invoke a recipe is
so huge compared to the time needed to reserve a semaphore that it is
insignificant in comparison.
The amount of contention is limited by -j i.e. by how many processes
there are ( 2 * CPUs is usually considered reasonable) and by how long
2x is too much. 1.5x has been the best in my experience, any more than that
and you're losing too much CPU to scheduling overhead instead of real work.
Any less and you're giving up too much in idle or I/O time.
--
-- Howard Chu
CTO, Symas Corp. http://www.symas.com
Director, Highland Sun http://highlandsun.com/hyc/
Chief Architect, OpenLDAP http://www.openldap.org/project/
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