linux-kernel - Re: [PATCH 1/2] sched: make nr_running() return "unsigned int"

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Message-ID: <20200312104427.GR12561@hirez.programming.kicks-ass.net>
Date:   Thu, 12 Mar 2020 11:44:27 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     mingo@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] sched: make nr_running() return "unsigned int"

On Thu, Mar 12, 2020 at 12:06:08AM +0300, Alexey Dobriyan wrote:
> I don't anyone have been crazy enough to spawn 2^32 threads.
> It'd require absurd amounts of physical memory.

And we're going to 5 level page-tables because 48 bits physical isn't
enough. 57 bits of physical is plenty space to spawn that many tasks and
still have some left over.

Now 32 bit tasks is indeed insane, but memory isn't the problem. The
actual limit is the pid-space, which is 30 bits.