Re: [PATCH 2.6.20-rc4 1/4] futex priority based wakeup

[Ulrich Drepper <drepper@redhat.com>]

Pierre Peiffer wrote:
> But there can be a performance impact when several processes use
> different futexes which have the same hash key.
> In fact, the plist contains all waiters _of_all_futexes_ having the same
> hash key, not only the waiters of a given futex. This can be more a
> problem,

s/can be/is/

There are systems with thousands of active futexes, maybe tens of
thousands.  Not only is hash collision likely, it's also a matter of
using and administering the plist.  We have to make futexes less
connected, not more.  Now I definitely want to see real world tests first.

-- 
➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖

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