Re: [PATCH] udev: Lower the starting children_max -> drop the minimum required RAM from 23mb to 5mb

On Sun, Jun 3, 2012 at 5:28 PM, Lauri Kasanen <[email protected]> wrote:
> Udev was the limiting factor for us on low-RAM systems.
> Given an average RSS of 180kb, 128 workers would require ~23mb of RAM.

All workers are direct clone()s of the master process without exec(),
you are sure that every of them uses additional 128k?

> Now, please consider what happens when there is only, say, 15mb free.
> Udev protects itself from OOM, and the kernel can do nothing but panic.

It does, if does not get started by systemd.

> 28 workers * 0.18mb = ~5mb. This change should not affect more powerful
> systems much, given that they still get the addition from the amount of RAM.

That logic is from the time we needed to fork() for every event. Even
on a system with lots of devices we usually do not need more than
30-50 workers. Today, workers are re-used; we could lower that limit
even more if needed, without bad side effects.

Applied.

Thanks,
Kay
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