linux-kernel - Re: [PATCH 2/2] futex: lockless wakeups

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Date:	Mon, 20 Apr 2015 10:31:05 -0700
From:	Davidlohr Bueso <dave@...olabs.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Chris Mason <clm@...com>, Steven Rostedt <rostedt@...dmis.org>,
	fredrik.markstrom@...driver.com, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] futex: lockless wakeups

On Mon, 2015-04-20 at 16:57 +0200, Peter Zijlstra wrote:
> Haha, you dug that out did you ;-)
> 
> Does this patch on its own actually help anything? Back when I wrote
> that there was the vague hope it would actually help some of the
> client-server ping-pong workloads, where the client does sync requests
> to the server.
> 
> In that case, if the server can handle the req. while the client yields
> we've saved on an expensive wakeup.
> 
> Reality never really worked out for that -- even after we fixed a few
> boot and runtime issues with it.

I had boot problems about 2 years ago (even with qemu) with it.
Nowadays, I cannot trigger any issues with it. And on a large machine
I've been using it just fine, throwing a lot of workloads at it. All in
all my schedule auditing has only been by searching the code, not from
this patch.

Thanks,
Davidlohr

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