Re: patch to support output synchronization under -j

[Howard Chu]

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/