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

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Message-ID: <5166D3F8.2050901@oracle.com>
Date:	Thu, 11 Apr 2013 11:17:12 -0400
From:	Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:	hpa@...or.com
CC:	mingo@...nel.org, linux-kernel@...r.kernel.org,
	konrad.wilk@...cle.com, boris.ostrovsky@...cle.com,
	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

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

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