linux-kernel - Re: [RFC PATCH] sched: rt: fix selecting runqueue for task to be pushed

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 linux-hardening linux-cve-announce 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:	Mon, 10 Dec 2012 09:21:13 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Hillf Danton <dhillf@...il.com>
Cc:	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH] sched: rt: fix selecting runqueue for task to be
 pushed

On Mon, 2012-12-10 at 20:19 +0800, Hillf Danton wrote:
> When we are trying to push task out, no point to select the last cpu that
> the given task executed on, which is fixed by selecting target cpu with
> cache affinity concerned, and with SD_WAKE_AFFINE ignored as we are not
> handling sleeper.

I have to ask. Why?

The check you are skipping is if the task is running on a CPU that is
already the lowest CPU priority (lowest_mask returns the CPUs running
tasks of the lowest priority in the system). Which means that either the
task that we are pushing is the same priority or lesser priority than
what is running on the other CPUs. Either case, this task wont push out
a task on the other CPUs because it's not higher priority than those
tasks.

You just added more work for the same result (no push).

-- Steve

--
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/