Re: [tip:x86/urgent] x86, mm: Patch out arch_flush_lazy_mmu_mode()when running on bare metal

From: Boris Ostrovsky
Date: Thu Apr 11 2013 - 11:17:10 EST


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@xxxxxxxxxx>
AuthorDate: Sat, 23 Mar 2013 09:36:36 -0400
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
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

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/