lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Sun, 14 Jul 2013 07:55:16 +0200
From:	Mike Galbraith <bitbucket@...ine.de>
To:	Kirill Tkhai <tkhai@...dex.ru>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH] sched: Add logic to handle parallel try_to_wake_up() of
 the same task

On Sat, 2013-07-13 at 19:45 +0400, Kirill Tkhai wrote: 
> This patch adds optimization of try_to_wake_up() function
> for cases when the system is doing parallel wake_up
> of the same task on the different cpus. Also it adds
> accounting the statistics of these situations.
> 
> We check the status of the task we want to wake up.
> If it is TASK_WAKING then the task is manipulated
> by try_to_wake_up() on another cpu. And after this
> check it will be a moment when the task is queued
> and his status is TASK_RUNNING. We just return
> earlier when we are sure the task will be TASK_RUNNING
> in the future (maybe right after the check). The profit is
> we don't loop while we are waiting the spinlock.

Hm, you're adding cycles to the common case to shave spin cycles in the
very rare case, then spending some to note that a collision happened.
What makes recording worth even 1 cycle?  What am I gonna do with the
knowledge that $dinkynum wakeups intersected at a some random task?

-Mike


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

Powered by blists - more mailing lists