linux-kernel - RE: [PATCH] Prevent immediate process rescheduling

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]

Message-ID: <DDE95BDD51FB774B804A9C029E735EE10379BEDA2F@sausexmbp02.amd.com>
Date:	Sun, 20 Sep 2009 16:03:23 -0500
From:	"Langsdorf, Mark" <mark.langsdorf@....com>
To:	"'Avi Kivity'" <avi@...hat.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
CC:	Ingo Molnar <mingo@...e.hu>, Mike Galbraith <efault@....de>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] Prevent immediate process rescheduling

> > Really hate this change though,. doesn't seem right to not 
> pick the same
> > task again if its runnable. Bad for cache footprint.
> 
> I agree, yielding should be explicitly requested.
> 
> Also, on a heavily overcommitted box an undirected yield might take 
> quite a long time to find the thread that's holding the lock. 
>  I think a 
> yield_to() will be a lot better:
> 
> - we can pick one of the vcpus belonging to the same guest to improve 
> the probability that the lock actually get released

Is there a way to find the other vcpus belonging to the
same guest?  I poked around at that, but couldn't find
one.

> - we avoid an issue when the other vcpus are on different 
> runqueues (in which case the current patch does nothing)
> - we can fix the accounting by donating vruntime from current to the 
> yielded-to vcpu

I may need someone to walk me through the vruntime donation
but that's secondary to finding the other vcpus.

-Mark Langsdorf
Operating System Research Center
AMD
--
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/