linux-kernel - Re: [PATCH 0/4] Fix ebizzy performance regression due to X86 TLB range flush v2

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:	Fri, 20 Dec 2013 12:18:18 +0100
From:	Ingo Molnar <mingo@...nel.org>
To:	Mel Gorman <mgorman@...e.de>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Alex Shi <alex.shi@...aro.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Fengguang Wu <fengguang.wu@...el.com>,
	H Peter Anvin <hpa@...or.com>, Linux-X86 <x86@...nel.org>,
	Linux-MM <linux-mm@...ck.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [PATCH 0/4] Fix ebizzy performance regression due to X86 TLB
 range flush v2


* Mel Gorman <mgorman@...e.de> wrote:

> On Thu, Dec 19, 2013 at 05:49:25PM +0100, Ingo Molnar wrote:
> > 
> > * Mel Gorman <mgorman@...e.de> wrote:
> > 
> > > [...]
> > > 
> > > Because we lack data on TLB range flush distributions I think we 
> > > should still go with the conservative choice for the TLB flush 
> > > shift. The worst case is really bad here and it's painfully obvious 
> > > on ebizzy.
> > 
> > So I'm obviously much in favor of this - I'd in fact suggest 
> > making the conservative choice on _all_ CPU models that have 
> > aggressive TLB range values right now, because frankly the testing 
> > used to pick those values does not look all that convincing to me.
> 
> I think the choices there are already reasonably conservative. I'd 
> be reluctant to support merging a patch that made a choice on all 
> CPU models without having access to the machines to run tests on. I 
> don't see the Intel people volunteering to do the necessary testing.

So based on this thread I lost confidence in test results on all CPU 
models but the one you tested.

I see two workable options right now:

 - We turn the feature off on all other CPU models, until someone
   measures and tunes them reliably.

or

 - We make all tunings that are more aggressive than yours to match
   yours. In the future people can measure and argue for more
   aggressive tunings.

Thanks,

	Ingo
--
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/