---------- Forwarded message ---------- From: Chiheng Xu <chiheng...@gmail.com> Date: Fri, Jul 30, 2010 at 6:02 PM Subject: Re: [RFC]serialize the output of parallel make? To: Tim Murphy <tnmur...@gmail.com>
On Fri, Jul 30, 2010 at 5:54 PM, Tim Murphy <tnmur...@gmail.com> 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 > the lock is held for which is basically about how long GNU make takes > to read the output from the process that currently has the lock. > Since modern computers have <1000s of CPUs the degree of contention is > not high and most of the cost of contention is something you pay for > no matter what method you use to descramble stuff. > > Our experience indicates that it performs very well. > If my guess is not wrong, the semaphore safeguard the consistency of output of one command, not the order of commands. -- Chiheng Xu Wuhan,China -- Chiheng Xu Wuhan,China _______________________________________________ Bug-make mailing list Bug-make@gnu.org http://lists.gnu.org/mailman/listinfo/bug-make
