From: Jason Gunthorpe <jgg@ziepe.ca>
To: David Hildenbrand <david@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
Andrew Dona-Couch <andrew@donacou.ch>,
Andrew Morton <akpm@linux-foundation.org>,
Drew DeVault <sir@cmpwn.com>,
Ammar Faizi <ammarfaizi2@gnuweeb.org>,
linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
io_uring Mailing List <io-uring@vger.kernel.org>,
Pavel Begunkov <asml.silence@gmail.com>,
linux-mm@kvack.org
Subject: Re: [PATCH] Increase default MLOCK_LIMIT to 8 MiB
Date: Tue, 23 Nov 2021 09:25:23 -0400 [thread overview]
Message-ID: <20211123132523.GA5112@ziepe.ca> (raw)
In-Reply-To: <5f998bb7-7b5d-9253-2337-b1d9ea59c796@redhat.com>
On Mon, Nov 22, 2021 at 09:08:47PM +0100, David Hildenbrand wrote:
> > You can't use mmu notifiers without impacting the fast path. This isn't
> > just about io_uring, there are other users of memlock right now (like
> > bpf) which just makes it even worse.
>
> 1) Do we have a performance evaluation? Did someone try and come up with
> a conclusion how bad it would be?
It needs additional locking between page readers and the mmu notifier.
One of the virtio things does this thing and they used rcu on the page
readers and a synchronize rcu in a mmu notifier - which I think is
pretty bad.
> 2) Could be provide a mmu variant to ordinary users that's just good
> enough but maybe not as fast as what we have today? And limit
> FOLL_LONGTERM to special, privileged users?
rdma has never been privileged
Jason
next prev parent reply other threads:[~2021-11-23 13:25 UTC|newest]
Thread overview: 58+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-28 8:08 [PATCH] Increase default MLOCK_LIMIT to 8 MiB Drew DeVault
2021-10-28 18:22 ` Jens Axboe
2021-11-04 14:27 ` Cyril Hrubis
2021-11-04 14:44 ` Jens Axboe
2021-11-06 2:33 ` Ammar Faizi
2021-11-06 7:05 ` Drew DeVault
2021-11-06 7:12 ` Ammar Faizi
2021-11-16 4:35 ` Andrew Morton
2021-11-16 6:32 ` Drew DeVault
2021-11-16 19:47 ` Andrew Morton
2021-11-16 19:48 ` Drew DeVault
2021-11-16 21:37 ` Andrew Morton
2021-11-17 8:23 ` Drew DeVault
2021-11-22 17:11 ` David Hildenbrand
2021-11-22 17:55 ` Andrew Dona-Couch
2021-11-22 18:26 ` David Hildenbrand
2021-11-22 19:53 ` Jens Axboe
2021-11-22 20:03 ` Matthew Wilcox
2021-11-22 20:04 ` Jens Axboe
2021-11-22 20:08 ` David Hildenbrand
2021-11-22 20:44 ` Jens Axboe
2021-11-22 21:56 ` David Hildenbrand
2021-11-23 12:02 ` David Hildenbrand
2021-11-23 13:25 ` Jason Gunthorpe [this message]
2021-11-23 13:39 ` David Hildenbrand
2021-11-23 14:07 ` Jason Gunthorpe
2021-11-23 14:44 ` David Hildenbrand
2021-11-23 17:00 ` Jason Gunthorpe
2021-11-23 17:04 ` David Hildenbrand
2021-11-23 22:04 ` Vlastimil Babka
2021-11-23 23:59 ` Jason Gunthorpe
2021-11-24 8:57 ` David Hildenbrand
2021-11-24 13:23 ` Jason Gunthorpe
2021-11-24 13:25 ` David Hildenbrand
2021-11-24 13:28 ` Jason Gunthorpe
2021-11-24 13:29 ` David Hildenbrand
2021-11-24 13:48 ` Jason Gunthorpe
2021-11-24 14:14 ` David Hildenbrand
2021-11-24 15:34 ` Jason Gunthorpe
2021-11-24 16:43 ` David Hildenbrand
2021-11-24 18:35 ` Jason Gunthorpe
2021-11-24 19:09 ` David Hildenbrand
2021-11-24 23:11 ` Jason Gunthorpe
2021-11-30 15:52 ` David Hildenbrand
2021-11-24 18:37 ` David Hildenbrand
2021-11-24 14:37 ` Vlastimil Babka
2021-11-24 14:41 ` David Hildenbrand
2021-11-16 18:36 ` Matthew Wilcox
2021-11-16 18:44 ` Drew DeVault
2021-11-16 18:55 ` Jens Axboe
2021-11-16 19:21 ` Vito Caputo
2021-11-16 19:25 ` Drew DeVault
2021-11-16 19:46 ` Vito Caputo
2021-11-16 19:41 ` Jens Axboe
2021-11-17 22:26 ` Johannes Weiner
2021-11-17 23:17 ` Jens Axboe
2021-11-18 21:58 ` Andrew Morton
2021-11-19 7:41 ` Drew DeVault
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