linux-kernel - Re: [PATCH v3 7/7] x86/tlb: add tlb_flushall

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Message-ID: <20120508152516.GF13568@aftab.osrc.amd.com>
Date:	Tue, 8 May 2012 17:25:16 +0200
From:	Borislav Petkov <bp@...64.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Alex Shi <alex.shi@...el.com>, mgorman@...e.de,
	npiggin@...il.com, tglx@...utronix.de, mingo@...hat.com,
	arnd@...db.de, rostedt@...dmis.org, fweisbec@...il.com,
	jeremy@...p.org, gregkh@...uxfoundation.org, glommer@...hat.com,
	riel@...hat.com, luto@....edu, avi@...hat.com, len.brown@...el.com,
	dhowells@...hat.com, fenghua.yu@...el.com, yinghai@...nel.org,
	ak@...ux.intel.com, cpw@....com, steiner@....com,
	akpm@...ux-foundation.org, penberg@...nel.org, hughd@...gle.com,
	rientjes@...gle.com, kosaki.motohiro@...fujitsu.com,
	n-horiguchi@...jp.nec.com, paul.gortmaker@...driver.com,
	trenn@...e.de, tj@...nel.org, oleg@...hat.com, axboe@...nel.dk,
	kamezawa.hiroyu@...fujitsu.com, viro@...iv.linux.org.uk,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 7/7] x86/tlb: add tlb_flushall_factor into sysfs for
 user change

On Tue, May 08, 2012 at 08:20:25AM -0700, H. Peter Anvin wrote:
> On 05/08/2012 08:11 AM, Peter Zijlstra wrote:
> > On Tue, 2012-05-08 at 22:03 +0800, Alex Shi wrote:
> >> kernel will replace cr3 rewrite with invlpg when
> >> 	tlb flush entries <= 1/tlb_flushall_factor
> >> if tlb_flushall_factor is 0, kernel won't do this replace.
> >>
> >> User can modify its value according to specific applications.
> > 
> > Yay!, another useless config knob :-(
> > 
> 
> I think this one is mostly for benchmarking new silicon to find out the
> proper value, I'm guessing?

Yep, this was supposed to be for pinpointing the proper entries count.
I believe we don't have this thing of having code intree but not really
intree - only for testing new silicon. Maybe a debug module or add this
to debugfs?

-- 
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Boris.

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