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From: Michal Hocko <mhocko@kernel.org>
To: Yang Shi <yang.shi@linux.alibaba.com>
Cc: akpm@linux-foundation.org, linux-mm@kvack.org,
	linux-kernel@vger.kernel.org
Subject: Re: [RFC PATCH 1/8] mm: mmap: unmap large mapping by section
Date: Thu, 22 Mar 2018 17:12:46 +0100	[thread overview]
Message-ID: <20180322161246.GG23100@dhcp22.suse.cz> (raw)
In-Reply-To: <8b4407dd-78f6-2f6f-3f45-ddb8a2d805c8@linux.alibaba.com>

On Thu 22-03-18 09:06:14, Yang Shi wrote:
> 
> 
> On 3/22/18 2:10 AM, Michal Hocko wrote:
> > On Wed 21-03-18 15:36:12, Yang Shi wrote:
> > > 
> > > On 3/21/18 2:23 PM, Michal Hocko wrote:
[...]
> > > > pages and that is quite easy to move out of the write lock. That would
> > > > be an improvement already and it should be risk safe. If even that is
> > > > not sufficient then using range locking should help a lot. There
> > > > shouldn't be really any other address space operations within the range
> > > > most of the time so this would be basically non-contended access.
> > > It might depend on how the range is defined. Too big range may lead to
> > > surprisingly more contention, but too small range may bring in too much
> > > lock/unlock operations.
> > The full vma will have to be range locked. So there is nothing small or large.
> 
> It sounds not helpful to a single large vma case since just one range lock
> for the vma, it sounds equal to mmap_sem.

This is not how the range locking works. If we have a range lock per mm
then exclusive ranges are not contending. So if you are unmapping one
vma and want to create a new mapping or fault into a different range
then you are basically lockless.

-- 
Michal Hocko
SUSE Labs

  reply	other threads:[~2018-03-22 16:12 UTC|newest]

Thread overview: 41+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-03-20 21:31 [RFC PATCH 0/8] Drop mmap_sem during unmapping large map Yang Shi
2018-03-20 21:31 ` [RFC PATCH 1/8] mm: mmap: unmap large mapping by section Yang Shi
2018-03-21 13:08   ` Michal Hocko
2018-03-21 16:31     ` Yang Shi
2018-03-21 17:29       ` Matthew Wilcox
2018-03-21 21:45         ` Yang Shi
2018-03-21 22:15           ` Matthew Wilcox
2018-03-21 22:40             ` Yang Shi
2018-03-21 22:46           ` Matthew Wilcox
2018-03-22 15:32             ` Laurent Dufour
2018-03-22 15:40               ` Matthew Wilcox
2018-03-22 15:54                 ` Laurent Dufour
2018-03-22 16:05                   ` Matthew Wilcox
2018-03-22 16:18                     ` Laurent Dufour
2018-03-22 16:46                       ` Yang Shi
2018-03-23 13:03                         ` Laurent Dufour
2018-03-22 16:51                       ` Matthew Wilcox
2018-03-22 16:49                     ` Yang Shi
2018-03-22 17:34         ` Yang Shi
2018-03-22 18:48           ` Matthew Wilcox
2018-03-24 18:24         ` Jerome Glisse
2018-03-21 13:14   ` Michal Hocko
2018-03-21 16:50     ` Yang Shi
2018-03-21 17:16       ` Yang Shi
2018-03-21 21:23         ` Michal Hocko
2018-03-21 22:36           ` Yang Shi
2018-03-22  9:10             ` Michal Hocko
2018-03-22 16:06               ` Yang Shi
2018-03-22 16:12                 ` Michal Hocko [this message]
2018-03-22 16:13                 ` Matthew Wilcox
2018-03-22 16:28                   ` Laurent Dufour
2018-03-22 16:36                     ` David Laight
2018-03-20 21:31 ` [RFC PATCH 2/8] mm: mmap: pass atomic parameter to do_munmap() call sites Yang Shi
2018-03-20 21:31 ` [RFC PATCH 3/8] mm: mremap: pass atomic parameter to do_munmap() Yang Shi
2018-03-20 21:31 ` [RFC PATCH 4/8] mm: nommu: add " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 5/8] ipc: shm: pass " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 6/8] fs: proc/vmcore: " Yang Shi
2018-03-20 21:31 ` [RFC PATCH 7/8] x86: mpx: " Yang Shi
2018-03-20 22:35   ` Thomas Gleixner
2018-03-21 16:53     ` Yang Shi
2018-03-20 21:31 ` [RFC PATCH 8/8] x86: vma: " Yang Shi

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