From: Jens Axboe <axboe@kernel.dk>
To: David Howells <dhowells@redhat.com>, John Hubbard <jhubbard@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
David Hildenbrand <david@redhat.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Logan Gunthorpe <logang@deltatee.com>,
Jeff Layton <jlayton@kernel.org>,
linux-block@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [GIT PULL] iov_iter: Improve page extraction (pin or just list)
Date: Mon, 30 Jan 2023 15:15:42 -0700 [thread overview]
Message-ID: <f392399b-a4c4-2251-e12b-e89fff351c4d@kernel.dk> (raw)
In-Reply-To: <3520518.1675116740@warthog.procyon.org.uk>
On 1/30/23 3:12 PM, David Howells wrote:
> John Hubbard <jhubbard@nvidia.com> wrote:
>
>> This is something that we say when adding pin_user_pages_fast(),
>> yes. I doubt that I can quickly find the email thread, but we
>> measured it and weren't immediately able to come up with a way
>> to make it faster.
>
> percpu counters maybe - add them up at the point of viewing?
They are percpu, see my last email. But for every 108 changes (on
my system), they will do two atomic_long_adds(). So not very
useful for anything but low frequency modifications.
--
Jens Axboe
next prev parent reply other threads:[~2023-01-30 22:15 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-01-30 11:14 David Howells
2023-01-30 21:33 ` Jens Axboe
2023-01-30 21:55 ` Jens Axboe
2023-01-30 21:57 ` Jens Axboe
2023-01-30 22:02 ` John Hubbard
2023-01-30 22:11 ` Jens Axboe
2023-01-30 22:12 ` David Howells
2023-01-30 22:15 ` Jens Axboe [this message]
2023-01-31 8:32 ` David Hildenbrand
2023-01-31 12:28 ` Jan Kara
2023-01-31 17:54 ` John Hubbard
2023-01-31 13:41 ` David Howells
2023-01-31 13:48 ` David Hildenbrand
2023-01-31 14:50 ` Jens Axboe
2023-01-31 15:02 ` David Hildenbrand
2023-01-31 15:04 ` Jens Axboe
2023-01-31 15:10 ` David Hildenbrand
2023-01-31 15:15 ` Jens Axboe
2023-01-30 21:52 ` David Howells
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