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

[Chiheng Xu]

---------- 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
> 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