Re: [PATCH 2/2] build-many-glibcs: Impose a memory limit on build processes.

[Zack Weinberg <zackw at panix dot com>]

On Mon, Jul 10, 2017 at 6:48 AM, Joseph Myers <joseph@codesourcery.com> wrote:
> On Sun, 9 Jul 2017, Zack Weinberg wrote:
>
>> The limit can be configured with the --memory-limit command line switch.
>> The default is 1.5 gigabytes or physical RAM divided by the number of
>> jobs to run in parallel, whichever is larger.  (Empirically, 1.5 gigs
>> per process is enough for everything but the files affected by GCC
>> bug 78640, but 1 gig per process is insufficient for some of the math
>> tests and also for the "genautomata" step when building compilers for
>> powerpc64.)
>
> I think the default should allow more room than just being slightly above
> what's enough right now in a particular build (does --enable-checking,
> i.e. GCC mainline, use more memory? I don't know offhand) - say 3 GB.
> (The default may be different from the threshold for the warning for
> values expected to be too small.)

So I actually wanted to make it _lower_ -- my usual build machine has
8 CPUs and 8G of RAM, so anything higher than 1G/concurrent process
risks going into swap.  But then genautomata. :-(

I think what I'll do -- after the powerpc situation is resolved -- is
put together some instrumentation to find out how much RAM is used
both on average and at worst; that will let us make more informed
decisions about the defaults.  I'll try GCC mainline as well.

>> +           gigabytes, whichever is larger.  (1GB is too small for
>> +           genautomata on MIPS and for the compilation of several
>> +           large math test cases.)
>
> Is it both powerpc64 and MIPS that need more than 1 GB, then?

No, it's just powerpc64, that's a mistake in the comment.

zw