Re: Fwd: [RFC]serialize the output of parallel make?

[Howard Chu]

Chiheng Xu wrote:
> ---------- Forwarded message ----------
> From: Chiheng Xu<address@hidden>
> Date: Fri, Jul 30, 2010 at 6:02 PM
> Subject: Re: [RFC]serialize the output of parallel make?
> To: Tim Murphy<address@hidden>
>
>
> On Fri, Jul 30, 2010 at 5:54 PM, Tim Murphy<address@hidden>  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/