linux-kernel - Re: [tip:x86/urgent] x86, mm: Patch out arch_flush_lazy_mmu

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Message-ID: <lkvk8wgl00gj6ba39c8n7j68.1365694922569@email.android.com>
Date:	Thu, 11 Apr 2013 11:42:02 -0400
From:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, jwboyer@...hat.com,
	tglx@...utronix.de, bp@...e.de
Subject: Re: [tip:x86/urgent] x86, mm: Patch out arch_flush_lazy_mmu_mode()
 when running on bare metal

I am sorry for top posting. Haven't figured out how to reply inline in the Android email client.

Boris, could you repost it please? If I recall correctly the only question on that patch was whether to put stable@...r.kernel.org on it and it was decided (by Greg) that was OK.

It is not an urgent patch though as it is only exposed with debug kernels.

Boris Ostrovsky <boris.ostrovsky@...cle.com> wrote:

>On 04/10/2013 08:30 PM, tip-bot for Boris Ostrovsky wrote:
>> Commit-ID:  511ba86e1d386f671084b5d0e6f110bb30b8eeb2
>> Gitweb:     http://git.kernel.org/tip/511ba86e1d386f671084b5d0e6f110bb30b8eeb2
>> Author:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
>> AuthorDate: Sat, 23 Mar 2013 09:36:36 -0400
>> Committer:  H. Peter Anvin <hpa@...ux.intel.com>
>> CommitDate: Wed, 10 Apr 2013 11:25:10 -0700
>>
>> x86, mm: Patch out arch_flush_lazy_mmu_mode() when running on bare metal
>>
>> Invoking arch_flush_lazy_mmu_mode() results in calls to
>> preempt_enable()/disable() which may have performance impact.
>>
>> Since lazy MMU is not used on bare metal we can patch away
>> arch_flush_lazy_mmu_mode() so that it is never called in such
>> environment.
>>
>> [ hpa: the previous patch "Fix vmalloc_fault oops during lazy MMU
>>    updates" may cause a minor performance regression on
>>    bare metal.  This patch resolves that performance regression.  It is
>>    somewhat unclear to me if this is a good -stable candidate. ]
>
>I think this
>
>    https://lkml.org/lkml/2013/2/26/420
>
>was also part of lazy mmu set of patches but is missing in the latest 
>batch of
>commits.
>
>-boris
>