Re: [patch] lockless, scalable get_pid(), for_each_process() elimination, 2.5.35-BK

From: Linus Torvalds (torvalds@transmeta.com)
Date: Wed Sep 18 2002 - 11:53:59 EST

On Wed, 18 Sep 2002, Rik van Riel wrote:
>
> On second thought ... yes there's a reason. Suppose you have
> 100000 threads on your box already, how long is it going to
> take to walk them all to figure out the pid distribution ?
>
> And are you willing to walk 100000 threads for every 16 pids allocated ?

Give me a real-life case where that happens, and I might care. I dare you.

The pid space is not a uniform distribution, which your made-up-example
depends on. So you usually walk the 100000 threads _once_, and then you
don't have to walk them again for quite a long time.

And guys, if this is a performance problem for some extreme site, the fix
is truly trivial:

        echo $((0x7fffffff)) > /proc/sys/max_pid

and you're done.

You're completely making up a problem that is not a problem in real life.
Come back to me when the above doesn't work _in_practice_ and somebody is
actually bitten, and maybe I'll care.

Until then, all you're doing is mental masturbation.

                Linus

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