From: Jan Kara <jack@suse.cz>
To: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Peter Xu <peterx@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
John Hubbard <jhubbard@nvidia.com>,
Leon Romanovsky <leonro@nvidia.com>,
Linux-MM <linux-mm@kvack.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"Maya B . Gokhale" <gokhale2@llnl.gov>,
Yang Shi <yang.shi@linux.alibaba.com>,
Marty Mcfadden <mcfadden8@llnl.gov>,
Kirill Shutemov <kirill@shutemov.name>,
Oleg Nesterov <oleg@redhat.com>, Jann Horn <jannh@google.com>,
Jan Kara <jack@suse.cz>, Kirill Tkhai <ktkhai@virtuozzo.com>,
Andrea Arcangeli <aarcange@redhat.com>,
Christoph Hellwig <hch@lst.de>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH 1/4] mm: Trial do_wp_page() simplification
Date: Fri, 18 Sep 2020 11:44:39 +0200 [thread overview]
Message-ID: <20200918094439.GD18920@quack2.suse.cz> (raw)
In-Reply-To: <20200917220900.GO8409@ziepe.ca>
On Thu 17-09-20 19:09:00, Jason Gunthorpe wrote:
> On Thu, Sep 17, 2020 at 05:40:59PM -0400, Peter Xu wrote:
> > On Thu, Sep 17, 2020 at 01:35:56PM -0700, Linus Torvalds wrote:
> > > For that to happen, we'd need to have the vma flag so that we wouldn't
> > > have any worry about non-pinners, but as you suggested, I think even
> > > just a mm-wide counter - or flag - to deal with the fast-bup case is
> > > likely perfectly sufficient.
> >
> > Would mm_struct.pinned_vm suffice?
>
> I think that could be a good long term goal
>
> IIRC last time we dug into the locked_vm vs pinned_vm mess it didn't
> get fixed. There is a mix of both kinds, as you saw, and some
> resistance I don't clearly remember to changing it.
>
> My advice for this -rc fix is to go with a single bit in the mm_struct
> set on any call to pin_user_pages*
>
> Then only users using pin_user_pages and forking are the only ones who
> would ever do extra COW on fork. I think that is OK for -rc, this
> workload should be rare due to the various historical issues. Anyhow,
> a slow down regression is better than a it is broken regression.
Agreed. I really like the solution of not write-protecting pinned pages on
fork(2).
> This can be improved into a counter later. Due to the pinned_vm
> accounting all call sites should have the mm_struct at unpin, but I
> have a feeling it will take a alot of driver patches to sort it all
> out.
I somewhat fear that some of the users of pin_user_pages() don't bother
with pinned_vm accounting exactly because they don't have mm_struct on
unpin...
Honza
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2020-09-18 9:44 UTC|newest]
Thread overview: 114+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-21 23:49 [PATCH 0/4] mm: Simplfy cow handling Peter Xu
2020-08-21 23:49 ` [PATCH 1/4] mm: Trial do_wp_page() simplification Peter Xu
2020-08-24 8:36 ` Kirill Tkhai
2020-08-24 14:30 ` Jan Kara
2020-08-24 15:37 ` Kirill Tkhai
2020-08-24 18:22 ` Linus Torvalds
2020-08-24 18:22 ` Linus Torvalds
2020-09-01 7:01 ` Hugh Dickins
2020-09-01 7:01 ` Hugh Dickins
2020-09-14 14:38 ` Jason Gunthorpe
2020-09-14 17:32 ` Linus Torvalds
2020-09-14 17:32 ` Linus Torvalds
2020-09-14 18:34 ` Peter Xu
2020-09-14 21:15 ` Peter Xu
2020-09-14 22:55 ` Jason Gunthorpe
2020-09-14 22:59 ` Linus Torvalds
2020-09-14 22:59 ` Linus Torvalds
2020-09-14 23:28 ` Jason Gunthorpe
2020-09-15 0:19 ` Linus Torvalds
2020-09-15 0:19 ` Linus Torvalds
2020-09-15 14:50 ` Peter Xu
2020-09-15 15:17 ` Peter Xu
2020-09-15 16:05 ` Jason Gunthorpe
2020-09-15 18:29 ` Jason Gunthorpe
2020-09-15 19:13 ` Peter Xu
2020-09-15 19:38 ` Jason Gunthorpe
2020-09-15 21:33 ` Peter Xu
2020-09-15 23:22 ` Jason Gunthorpe
2020-09-16 1:50 ` John Hubbard
2020-09-16 17:48 ` Jason Gunthorpe
2020-09-16 18:46 ` Peter Xu
2020-09-17 11:25 ` Jason Gunthorpe
2020-09-17 18:11 ` Linus Torvalds
2020-09-17 18:11 ` Linus Torvalds
2020-09-17 19:38 ` Jason Gunthorpe
2020-09-17 19:51 ` Linus Torvalds
2020-09-17 19:51 ` Linus Torvalds
2020-09-18 16:40 ` Peter Xu
2020-09-18 17:16 ` Linus Torvalds
2020-09-18 17:16 ` Linus Torvalds
2020-09-18 19:57 ` Peter Xu
2020-09-18 17:32 ` Jason Gunthorpe
2020-09-18 20:40 ` Peter Xu
2020-09-18 20:59 ` Linus Torvalds
2020-09-18 20:59 ` Linus Torvalds
2020-09-19 0:28 ` Jason Gunthorpe
2020-09-18 21:06 ` John Hubbard
2020-09-19 0:01 ` Jason Gunthorpe
2020-09-21 8:35 ` Jan Kara
2020-09-21 12:03 ` Jason Gunthorpe
2022-02-16 16:59 ` Oded Gabbay
2022-02-16 17:24 ` Oded Gabbay
2022-02-16 19:04 ` Linus Torvalds
2022-02-16 19:20 ` Oded Gabbay
2022-02-16 19:24 ` David Hildenbrand
2020-09-21 13:42 ` Michal Hocko
2020-09-21 14:18 ` Peter Xu
2020-09-21 14:28 ` Michal Hocko
2020-09-21 14:38 ` Tejun Heo
2020-09-21 14:43 ` Christian Brauner
2020-09-21 14:55 ` Michal Hocko
2020-09-21 15:04 ` Christian Brauner
2020-09-21 16:06 ` Michal Hocko
2020-09-23 7:53 ` Michal Hocko
2020-09-21 14:41 ` Christian Brauner
2020-09-21 14:57 ` Michal Hocko
2020-09-21 16:31 ` Peter Xu
2020-09-17 18:14 ` Peter Xu
2020-09-17 18:26 ` Linus Torvalds
2020-09-17 18:26 ` Linus Torvalds
2020-09-17 19:03 ` Peter Xu
2020-09-17 19:42 ` Linus Torvalds
2020-09-17 19:42 ` Linus Torvalds
2020-09-17 19:55 ` John Hubbard
2020-09-17 20:06 ` Jason Gunthorpe
2020-09-17 20:19 ` John Hubbard
2020-09-17 20:25 ` Jason Gunthorpe
2020-09-17 20:35 ` Linus Torvalds
2020-09-17 20:35 ` Linus Torvalds
2020-09-17 21:40 ` Peter Xu
2020-09-17 22:09 ` Jason Gunthorpe
2020-09-17 22:25 ` Linus Torvalds
2020-09-17 22:25 ` Linus Torvalds
2020-09-17 22:48 ` Ira Weiny
2020-09-18 9:36 ` Jan Kara
2020-09-18 9:44 ` Jan Kara [this message]
2020-09-18 16:19 ` Jason Gunthorpe
2020-09-15 10:23 ` Leon Romanovsky
2020-09-15 15:56 ` Jason Gunthorpe
2020-09-15 15:03 ` Oleg Nesterov
2020-09-15 16:18 ` Peter Xu
2020-08-21 23:49 ` [PATCH 2/4] mm/ksm: Remove reuse_ksm_page() Peter Xu
2020-08-21 23:49 ` [PATCH 3/4] mm/gup: Remove enfornced COW mechanism Peter Xu
2020-09-14 14:27 ` Oleg Nesterov
2020-09-14 17:59 ` Peter Xu
2020-09-14 19:03 ` Linus Torvalds
2020-09-14 19:03 ` Linus Torvalds
2020-08-21 23:49 ` [PATCH 4/4] mm: Add PGREUSE counter Peter Xu
2020-08-22 16:14 ` Linus Torvalds
2020-08-22 16:14 ` Linus Torvalds
2020-08-24 0:24 ` Peter Xu
2020-08-22 16:05 ` [PATCH 0/4] mm: Simplfy cow handling Linus Torvalds
2020-08-22 16:05 ` Linus Torvalds
2020-08-23 23:58 ` Peter Xu
2020-08-24 8:38 ` Kirill Tkhai
2020-08-27 14:15 ` Peter Xu
2021-02-02 14:40 [PATCH 1/4] mm: Trial do_wp_page() simplification Gal Pressman
2021-02-02 16:31 ` Peter Xu
2021-02-02 16:44 ` Jason Gunthorpe
2021-02-02 17:05 ` Peter Xu
2021-02-02 17:13 ` Jason Gunthorpe
2021-02-03 12:43 ` Gal Pressman
2021-02-03 14:00 ` Jason Gunthorpe
2021-02-03 14:47 ` Gal Pressman
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