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Re: patch to support output synchronization under -j

From: Howard Chu
Subject: Re: patch to support output synchronization under -j
Date: Fri, 15 Apr 2011 11:32:02 -0700
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Eli Zaretskii wrote:
Date: Fri, 15 Apr 2011 10:37:13 -0400
From: David Boyce<address@hidden>
it's more a question of how many parallel jobs a given make process is
managing since limits on file handles/descriptors are per process.

What about people who use "make -j" without limits?

They're idiots. I've never seen a machine that can handle more than 1.5x number of cores without getting bottlenecked by I/O or system scheduler. (And I've run this stuff on 1024 node Connection Machines, among other things...) Go above a certain threshold and you're only slowing yourself down.

It's not like having a 256-core machine is a fantasy that will not
happen in a few years.  On my day job, we are already using 12 cores
and don't consider that "living on the edge".

We've already seen bug reports from people running on machines with 4096 cores, trying to run with -j8192 or somesuch. (Default pipe buffer is 4K which sets -j4096 as the practical limit without mucking with kernel params.)

  -- 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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