linux-kernel - Re: [RFC,PATCH 0/2] do_wait() wakeup optimization

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Message-ID: <20090623143054.GA10069@redhat.com>
Date:	Tue, 23 Jun 2009 16:30:54 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ratan Nalumasu <rnalumasu@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Ingo Molnar <mingo@...e.hu>,
	Roland McGrath <roland@...hat.com>,
	Vitaly Mayatskikh <vmayatsk@...hat.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC,PATCH 0/2] do_wait() wakeup optimization

On 06/23, Ratan Nalumasu wrote:
>
> Yes, it is something we really need. The specific case I have (hundreds of
> NTPL threads in a program, and each thread managing a child process), the
> CPU load is >99% with NTPL threads, near 0% with the patch
                                                   ^^^^^^^^^

Thanks. Did you test this patch, or do you mean the previous one?

> So, yes, the complication is worthwhile.

I am asking because I am not sure this change is enough, note the
"We can make child_wait_callback() more clever later" in the changelog.

__wake_up_parent() passes key = p, but we can pass more info and do
additional checks in child_wait_callback().

Oleg.

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