From: Matthew Wilcox <willy@infradead.org>
To: Steven Sistare <steven.sistare@oracle.com>
Cc: Khalid Aziz <khalid.aziz@oracle.com>,
akpm@linux-foundation.org, david@redhat.com,
ying.huang@intel.com, mgorman@techsingularity.net,
baolin.wang@linux.alibaba.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Khalid Aziz <khalid@kernel.org>
Subject: Re: [PATCH v4] mm, compaction: Skip all non-migratable pages during scan
Date: Thu, 25 May 2023 22:31:15 +0100 [thread overview]
Message-ID: <ZG/To8Z3StoVoenU@casper.infradead.org> (raw)
In-Reply-To: <ZG/I7tYY4uV/32hP@casper.infradead.org>
On Thu, May 25, 2023 at 09:45:34PM +0100, Matthew Wilcox wrote:
> > > Isn't "long term pinning" the wrong description of the problem? Long term
> > > pins suggest to me FOLL_LONGTERM. I think this is simple short term
> > > pins that we care about here.
> >
> > vfio pins are held for a long time - Steve
>
> So this is a third sense of "pinned pages" that is neither what
> filesystems nor the mm means by pinned pages, but whatever it is that
> vfio means by pinned pages? If only "pin" weren't such a desirable
> word. Can somebody explain to me in small words what a vfio pin looks
> like because I've tried reading vfio_iommu_type1_pin_pages() and I
> don't recognise anything there that looks like pinning in either of
> the other two senses.
Oh, I think I found it! pin_user_pages_remote() is called by
vaddr_get_pfns(). If these are the pages you're concerned about,
then the efficient way to do what you want is simply to call
folio_maybe_dma_pinned(). Far more efficient than the current mess
of total_mapcount().
next prev parent reply other threads:[~2023-05-25 21:31 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-25 19:15 [PATCH v4] mm, compaction: Skip all non-migratable pages during scan Khalid Aziz
2023-05-25 19:58 ` Matthew Wilcox
2023-05-25 20:15 ` Steven Sistare
2023-05-25 20:45 ` Matthew Wilcox
2023-05-25 21:31 ` Matthew Wilcox [this message]
2023-05-26 15:44 ` Khalid Aziz
2023-05-26 16:44 ` Matthew Wilcox
2023-05-26 16:46 ` David Hildenbrand
2023-05-26 18:46 ` Matthew Wilcox
2023-05-26 18:50 ` David Hildenbrand
2023-05-27 2:11 ` John Hubbard
2023-05-27 3:18 ` Matthew Wilcox
2023-05-28 23:49 ` John Hubbard
2023-05-29 0:31 ` Matthew Wilcox
2023-05-29 9:25 ` David Hildenbrand
2023-05-30 15:42 ` Khalid Aziz
2023-06-09 22:11 ` Andrew Morton
2023-06-09 23:28 ` Khalid Aziz
2023-05-25 20:41 ` Khalid Aziz
2023-05-29 3:01 ` Huang, Ying
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