Re: [gentoo-user] Jobs and load-average

[Rich Freeman]

On Wed, Feb 15, 2023 at 4:56 AM Peter Humphrey <peter@××××××××××××.uk> wrote:
>
> Not long ago I read that we should allow 2GB RAM for every emerge job - that
> is, we should divide our RAM size by 2 to get the maximum number of
> simultaneous jobs. I'm trying to get that right, but I'm not there yet.
>
> I have these entries in make.conf:
> EMERGE_DEFAULT_OPTS="--jobs=16 --load-average=32 --autounmask=n --quiet-
> unmerge-warn --ke>
> MAKEOPTS="-j16"
>
> Today, though, I saw load averages going up to 72. Can anyone suggest better
> values to suit my 24 threads and 64GB RAM?

First, keep in mind that --jobs=16 + -j16 can result in up to 256
(16*16) tasks running at once.  Of course, that is worst case and most
of the time you'll have way less than that.

Keep in mind that you need to consider available RAM and not just
total RAM.  Run free under the conditions where you typically run
emerge and see how much available memory it displays.  Depending on
what you have running it could be much lower than 64GB.

Beyond that, unfortunately this is hard to deal with beyond just
figuring out what needs more RAM and making exceptions in package.env.

Also, RAM pressure could also come from the build directory if it is
on tmpfs, which of course many of us use.

Some packages that I build with either a greatly reduced -j setting or
a non-tmpfs build directory are:
sys-cluster/ceph
dev-python/scipy
dev-python/pandas
app-office/calligra
net-libs/nodejs
dev-qt/qtwebengine
dev-qt/qtwebkit
dev-lang/spidermonkey
www-client/chromium
app-office/libreoffice
sys-devel/llvm
dev-lang/rust   (I use the rust binary these days as this has gotten
really out of hand)
x11-libs/gtk+

These are just packages I've had issues with at some point, and it is
possible that some of these packages no longer use as much memory
today.

-- 
Rich