linux-kernel - Re: [PATCH 3/3] futex: fix miss ordered wakeups

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Date:	Thu, 22 May 2008 22:36:27 -0700
From:	Daniel Walker <dwalker@...sta.com>
To:	Ulrich Drepper <drepper@...il.com>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] futex: fix miss ordered wakeups

On Thu, 2008-05-22 at 22:24 -0700, Ulrich Drepper wrote:
> On Thu, May 22, 2008 at 10:15 PM, Daniel Walker <dwalker@...sta.com> wrote:
> > That's the problem we aren't just covering 99.99% we're trying to cover
> > 100% of cases.. If we don't do it in that one case we may as well not do
> > it at all.
> 
> I have no problem with removing the other ordering.  It was added
> because it limited overhead.  It is completely wrong to have everybody
> pay for the needs for a very small minority.

I think that ordering is something companies have been wanting for a
long time.. I had a lot of people asking about it, I was glad when it
was added.. However, it all falls down in the one case which we don't
handle. 

I don't think the overhead for this is all that bad.. Consider that the
worst performance case is the contended case, and this patch adds a very
small amount of code. The vast majority of cases are un-contended , and
it's already know to be slow in the cases which are contended.

Daniel

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