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From: Alex Shi <alex.shi@intel.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Nick Piggin <npiggin@gmail.com>,
	tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com,
	arnd@arndb.de, rostedt@goodmis.org, fweisbec@gmail.com,
	jeremy@goop.org, riel@redhat.com, luto@mit.edu, avi@redhat.com,
	len.brown@intel.com, dhowells@redhat.com, fenghua.yu@intel.com,
	borislav.petkov@amd.com, yinghai@kernel.org, ak@linux.intel.com,
	cpw@sgi.com, steiner@sgi.com, akpm@linux-foundation.org,
	penberg@kernel.org, hughd@google.com, rientjes@google.com,
	kosaki.motohiro@jp.fujitsu.com, n-horiguchi@ah.jp.nec.com,
	tj@kernel.org, oleg@redhat.com, axboe@kernel.dk,
	jmorris@namei.org, kamezawa.hiroyu@jp.fujitsu.com,
	viro@zeniv.linux.org.uk, linux-kernel@vger.kernel.org,
	yongjie.ren@intel.com, linux-arch@vger.kernel.org
Subject: Re: [PATCH v5 6/7] x86/tlb: optimizing flush_tlb_mm
Date: Thu, 17 May 2012 08:43:45 +0800	[thread overview]
Message-ID: <4FB449C1.2020603@intel.com> (raw)
In-Reply-To: <1337202569.4281.13.camel@twins>

On 05/17/2012 05:09 AM, Peter Zijlstra wrote:

> On Wed, 2012-05-16 at 21:34 +0800, Alex Shi wrote:
>>
>> So, if the minimum change of tlb->start/end can be protected by
>> HAVE_GENERIC_MMU_GATHER, it is safe and harmless, am I right?
>>
> safe yes, but not entirely harmless. A quick look seems to suggest you
> fail for VM_HUGETLB. If your mmu_gather spans a vma with VM_HUGETLB
> you'll do a regular range flush not a full mm flush like the other paths
> do.


Thanks!
Uh, HUGETLB will be found by has_large_page() if THP enabled now. And I
will remove THP cost, then HUGETLB will be deal well. Since the max
number of TLB entries is 512, has_large_page just need execute once just
when the start address is align at HPAGE_SIZE.

IMHO, this patch enabled generic mmu range flush support with just teen
lines. and it is supported well by low level x86 architecture. I like it. :)

> 
> Anyway, I did a quick refresh of my series on a recent -tip tree:
> 
>  git://git.kernel.org/pub/scm/linux/kernel/git/peterz/mmu.git tlb-unify
> 
> With that all you need is to "select HAVE_MMU_GATHER_RANGE" for x86 and
> implement a useful flush_tlb_range().

> 
> In particular, see:
> http://git.kernel.org/?p=linux/kernel/git/peterz/mmu.git;a=commitdiff;h=05e53144177e6242fda404045f50f48114bcf185;hp=2cd7dc710652127522392f4b7ecb5fa6e954941e
> 
> I've slightly changed the code to address an open issue with the
> vm_flags tracking. We now force flush the mmu_gather whenever VM_HUGETLB
> flips because most (all?) archs that look at that flag expect pure huge
> pages and not a mixture.
> 
> I've seem to have misplaced my cross-compiler set, so I've only compiled
> x86-64 for now.


Oh, I also need a cross-compiler for other archs. Thanks reminder!

  reply	other threads:[~2012-05-17  0:45 UTC|newest]

Thread overview: 50+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-05-15  8:55 [PATCH v5 0/7] tlb flush optimization for x86 Alex Shi
2012-05-15  8:55 ` [PATCH v5 1/7] x86/tlb: unify TLB_FLUSH_ALL definition Alex Shi
2012-05-15  8:55 ` [PATCH v5 2/7] x86/tlb_info: get last level TLB entry number of CPU Alex Shi
2012-05-15  8:55 ` [PATCH v5 3/7] x86/flush_tlb: try flush_tlb_single one by one in flush_tlb_range Alex Shi
2012-05-15  8:55 ` [PATCH v5 4/7] x86/tlb: fall back to flush all when meet a THP large page Alex Shi
2012-05-15  8:55 ` [PATCH v5 5/7] x86/tlb: add tlb_flushall_shift for specific CPU Alex Shi
2012-05-16  6:49   ` Alex Shi
2012-05-16 17:55     ` H. Peter Anvin
2012-05-17  1:46       ` Alex Shi
2012-05-15  8:55 ` [PATCH v5 6/7] x86/tlb: optimizing flush_tlb_mm Alex Shi
2012-05-15  9:11   ` Peter Zijlstra
2012-05-15  9:15   ` Nick Piggin
2012-05-15  9:17     ` Nick Piggin
2012-05-15 12:58       ` Luming Yu
2012-05-15 13:06         ` Peter Zijlstra
2012-05-15 13:27           ` Luming Yu
2012-05-15 13:28             ` Alex Shi
2012-05-15 13:33           ` Alex Shi
2012-05-15 13:39           ` Steven Rostedt
2012-05-15 14:04             ` Borislav Petkov
2012-05-15 13:08         ` Luming Yu
2012-05-15 14:07       ` Alex Shi
2012-05-15  9:18     ` Peter Zijlstra
2012-05-15  9:52       ` Nick Piggin
2012-05-15 10:00         ` Peter Zijlstra
2012-05-15 10:06           ` Nick Piggin
2012-05-15 10:13             ` Peter Zijlstra
2012-05-15 14:04       ` Alex Shi
2012-05-15 13:24     ` Alex Shi
2012-05-15 14:36       ` Peter Zijlstra
2012-05-15 14:57         ` Peter Zijlstra
2012-05-15 15:01           ` Alex Shi
2012-05-16  6:46           ` Alex Shi
2012-05-16  6:46             ` Alex Shi
2012-05-16  8:00             ` Peter Zijlstra
2012-05-16  8:04               ` Peter Zijlstra
2012-05-16  8:53                 ` Alex Shi
2012-05-16  8:58                   ` Peter Zijlstra
2012-05-16 10:58                     ` Alex Shi
2012-05-16 11:04                       ` Peter Zijlstra
2012-05-16 12:57                         ` Alex Shi
2012-05-16 13:34               ` Alex Shi
2012-05-16 13:34                 ` Alex Shi
2012-05-16 21:09                 ` Peter Zijlstra
2012-05-17  0:43                   ` Alex Shi [this message]
2012-05-17  2:07                     ` Steven Rostedt
2012-05-17  8:04                       ` Alex Shi
2012-05-17  2:14                   ` Paul Mundt
2012-05-16 13:44               ` Alex Shi
2012-05-15  8:55 ` [PATCH v5 7/7] x86/tlb: add tlb_flushall_shift knob into debugfs Alex Shi

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