From: Jason Gunthorpe <jgg@ziepe.ca>
To: Chris Wilson <chris@chris-wilson.co.uk>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
intel-gfx@lists.freedesktop.org,
"Andrew Morton" <akpm@linux-foundation.org>,
"Jan Kara" <jack@suse.cz>, "Jérôme Glisse" <jglisse@redhat.com>,
"John Hubbard" <jhubbard@nvidia.com>,
"Claudio Imbrenda" <imbrenda@linux.ibm.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH] mm: Skip opportunistic reclaim for dma pinned pages
Date: Wed, 24 Jun 2020 16:21:16 -0300 [thread overview]
Message-ID: <20200624192116.GO6578@ziepe.ca> (raw)
In-Reply-To: <20200624191417.16735-1-chris@chris-wilson.co.uk>
On Wed, Jun 24, 2020 at 08:14:17PM +0100, Chris Wilson wrote:
> A general rule of thumb is that shrinkers should be fast and effective.
> They are called from direct reclaim at the most incovenient of times when
> the caller is waiting for a page. If we attempt to reclaim a page being
> pinned for active dma [pin_user_pages()], we will incur far greater
> latency than a normal anonymous page mapped multiple times. Worse the
> page may be in use indefinitely by the HW and unable to be reclaimed
> in a timely manner.
A pinned page can't be migrated, discarded or swapped by definition -
it would cause data corruption.
So, how do things even get here and/or work today at all? I think the
explanation is missing something important.
Jason
next prev parent reply other threads:[~2020-06-24 19:21 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-24 19:14 Chris Wilson
2020-06-24 19:21 ` Jason Gunthorpe [this message]
2020-06-24 20:23 ` Yang Shi
2020-06-24 21:02 ` Yang Shi
2020-06-24 20:23 ` Chris Wilson
2020-06-24 20:47 ` John Hubbard
2020-06-24 23:20 ` Jason Gunthorpe
2020-06-25 0:11 ` John Hubbard
2020-06-25 11:24 ` Jan Kara
2020-06-25 7:57 ` Michal Hocko
2020-06-25 11:00 ` Chris Wilson
2020-06-25 15:12 ` Michal Hocko
2020-06-25 15:48 ` Chris Wilson
2020-06-25 11:42 ` Matthew Wilcox
2020-06-25 13:40 ` Jan Kara
2020-06-25 16:05 ` Matthew Wilcox
2020-06-25 16:32 ` Yang Shi
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