From: David Howells <dhowells@redhat.com>
To: David Hildenbrand <david@redhat.com>
Cc: dhowells@redhat.com, Jens Axboe <axboe@kernel.dk>,
John Hubbard <jhubbard@nvidia.com>,
Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
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: Tue, 31 Jan 2023 13:41:30 +0000 [thread overview]
Message-ID: <3791872.1675172490@warthog.procyon.org.uk> (raw)
In-Reply-To: <040ed7a7-3f4d-dab7-5a49-1cd9933c5445@redhat.com>
David Hildenbrand <david@redhat.com> wrote:
> >> 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.
> >
>
> Can we just treat the whole acquired/released accounting as a debug mechanism
> to detect missing releases and do it only for debug kernels?
>
>
> The pcpu counter is an s8, so we have to flush on a regular basis and cannot
> really defer it any longer ... but I'm curious if it would be of any help to
> only have a single PINNED counter that goes into both directions (inc/dec on
> pin/release), to reduce the flushing.
>
> Of course, once we pin/release more than ~108 pages in one go or we switch
> CPUs frequently it won't be that much of a help ...
What are the stats actually used for? Is it just debugging, or do we actually
have users for them (control groups spring to mind)?
David
next prev parent reply other threads:[~2023-01-31 13:41 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
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 [this message]
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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