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From: "Kirill A. Shutemov" <kirill@shutemov.name>
To: John Hubbard <jhubbard@nvidia.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Williams" <dan.j.williams@intel.com>,
	"Dave Chinner" <david@fromorbit.com>,
	"Ira Weiny" <ira.weiny@intel.com>, "Jan Kara" <jack@suse.cz>,
	"Jason Gunthorpe" <jgg@ziepe.ca>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Jérôme Glisse" <jglisse@redhat.com>,
	"Michal Hocko" <mhocko@suse.com>,
	"Mike Kravetz" <mike.kravetz@oracle.com>,
	"Shuah Khan" <shuah@kernel.org>,
	"Vlastimil Babka" <vbabka@suse.cz>,
	"Matthew Wilcox" <willy@infradead.org>,
	linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-kselftest@vger.kernel.org, linux-rdma@vger.kernel.org,
	linux-mm@kvack.org, LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v4 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting
Date: Wed, 5 Feb 2020 14:43:25 +0300
Message-ID: <20200205114325.4e2f5aghsusihpap@box> (raw)
In-Reply-To: <20200204234117.2974687-11-jhubbard@nvidia.com>

On Tue, Feb 04, 2020 at 03:41:15PM -0800, John Hubbard wrote:
> Now that pages are "DMA-pinned" via pin_user_page*(), and unpinned via
> unpin_user_pages*(), we need some visibility into whether all of this is
> working correctly.
> 
> Add two new fields to /proc/vmstat:
> 
>     nr_foll_pin_acquired
>     nr_foll_pin_released
> 
> These are documented in Documentation/core-api/pin_user_pages.rst.
> They represent the number of pages (since boot time) that have been
> pinned ("nr_foll_pin_acquired") and unpinned ("nr_foll_pin_released"),
> via pin_user_pages*() and unpin_user_pages*().
> 
> In the absence of long-running DMA or RDMA operations that hold pages
> pinned, the above two fields will normally be equal to each other.
> 
> Also: update Documentation/core-api/pin_user_pages.rst, to remove an
> earlier (now confirmed untrue) claim about a performance problem with
> /proc/vmstat.
> 
> Also: updated Documentation/core-api/pin_user_pages.rst to rename the
> new /proc/vmstat entries, to the names listed here.
> 
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>

Please, clarify semantics for huge page. An user may want to know if we
count huge page as one pin-acquired or by number of pages.

Otherwise looks good (given Jan concern is addressed).

-- 
 Kirill A. Shutemov

  parent reply index

Thread overview: 21+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-04 23:41 [PATCH v4 00/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 01/12] mm: dump_page(): better diagnostics for compound pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 02/12] mm/gup: split get_user_pages_remote() into two routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 03/12] mm/gup: pass a flags arg to __gup_device_* functions John Hubbard
2020-02-04 23:41 ` [PATCH v4 04/12] mm: introduce page_ref_sub_return() John Hubbard
2020-02-05  9:23   ` Jan Kara
2020-02-05 11:23   ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 05/12] mm/gup: pass gup flags to two more routines John Hubbard
2020-02-04 23:41 ` [PATCH v4 06/12] mm/gup: require FOLL_GET for get_user_pages_fast() John Hubbard
2020-02-04 23:41 ` [PATCH v4 07/12] mm/gup: track FOLL_PIN pages John Hubbard
2020-02-05 11:35   ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 08/12] mm/gup: page->hpage_pinned_refcount: exact pin counts for huge pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 09/12] mm: dump_page(): better diagnostics for huge pinned pages John Hubbard
2020-02-04 23:41 ` [PATCH v4 10/12] mm/gup: /proc/vmstat: pin_user_pages (FOLL_PIN) reporting John Hubbard
2020-02-05  9:37   ` Jan Kara
2020-02-05 23:13     ` John Hubbard
2020-02-05 11:43   ` Kirill A. Shutemov [this message]
2020-02-05 23:58     ` John Hubbard
2020-02-04 23:41 ` [PATCH v4 11/12] mm/gup_benchmark: support pin_user_pages() and related calls John Hubbard
2020-02-05 11:46   ` Kirill A. Shutemov
2020-02-04 23:41 ` [PATCH v4 12/12] selftests/vm: run_vmtests: invoke gup_benchmark with basic FOLL_PIN coverage John Hubbard

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