19 Oct, 2020
1 commit
-
To be safe against concurrent changes to the VMA tree, we must take the
mmap lock around GUP operations (excluding the GUP-fast family of
operations, which will take the mmap lock by themselves if necessary).This code is only for testing, and it's only reachable by root through
debugfs, so this doesn't really have any impact; however, if we want to
add lockdep asserts into the GUP path, we need to have clean locking here.Signed-off-by: Jann Horn
Signed-off-by: Andrew Morton
Reviewed-by: Jason Gunthorpe
Reviewed-by: John Hubbard
Acked-by: Michel Lespinasse
Cc: "Eric W . Biederman"
Cc: Mauro Carvalho Chehab
Cc: Sakari Ailus
Link: https://lkml.kernel.org/r/CAG48ez3SG6ngZLtasxJ6LABpOnqCz5-QHqb0B4k44TQ8F9n6+w@mail.gmail.com
Signed-off-by: Linus Torvalds
14 Oct, 2020
1 commit
-
According to Documentation/core-api/pin_user_pages.rst, FOLL_PIN is a
prerequisite to FOLL_LONGTERM. Another way of saying that is,
FOLL_LONGTERM is a specific case, more restrictive case of FOLL_PIN.Almost all kernel modules are using pin_user_pages() with FOLL_LONGTERM,
mm/gup_benchmark.c seems to the only exception in which FOLL_PIN is not a
prerequisite to FOLL_LONGTERM.Signed-off-by: Barry Song
Signed-off-by: Andrew Morton
Reviewed-by: John Hubbard
Cc: Jan Kara
Cc: Jérôme Glisse
Cc: "Matthew Wilcox (Oracle)"
Cc: Al Viro
Cc: Christoph Hellwig
Cc: Dan Williams
Cc: Dave Chinner
Cc: Jason Gunthorpe
Cc: Jonathan Corbet
Cc: Michal Hocko
Cc: Mike Kravetz
Cc: Shuah Khan
Cc: Vlastimil Babka
Link: http://lkml.kernel.org/r/20200815122056.29508-1-song.bao.hua@hisilicon.com
Signed-off-by: Linus Torvalds
03 Apr, 2020
1 commit
-
Up until now, gup_benchmark supported testing of the following kernel
functions:* get_user_pages(): via the '-U' command line option
* get_user_pages_longterm(): via the '-L' command line option
* get_user_pages_fast(): as the default (no options required)Add test coverage for the new corresponding pin_*() functions:
* pin_user_pages_fast(): via the '-a' command line option
* pin_user_pages(): via the '-b' command line optionAlso, add an option for clarity: '-u' for what is now (still) the default
choice: get_user_pages_fast().Also, for the commands that set FOLL_PIN, verify that the pages really are
dma-pinned, via the new is_dma_pinned() routine. Those commands are:PIN_FAST_BENCHMARK : calls pin_user_pages_fast()
PIN_BENCHMARK : calls pin_user_pages()In between the calls to pin_*() and unpin_user_pages(), check each page:
if page_maybe_dma_pinned() returns false, then WARN and return.Do this outside of the benchmark timestamps, so that it doesn't affect
reported times.Signed-off-by: John Hubbard
Signed-off-by: Andrew Morton
Reviewed-by: Ira Weiny
Acked-by: Kirill A. Shutemov
Cc: Jan Kara
Cc: Jérôme Glisse
Cc: "Matthew Wilcox (Oracle)"
Cc: Al Viro
Cc: Christoph Hellwig
Cc: Dan Williams
Cc: Dave Chinner
Cc: Jason Gunthorpe
Cc: Jonathan Corbet
Cc: Michal Hocko
Cc: Mike Kravetz
Cc: Shuah Khan
Cc: Vlastimil Babka
Link: http://lkml.kernel.org/r/20200211001536.1027652-10-jhubbard@nvidia.com
Signed-off-by: Linus Torvalds
01 Feb, 2020
1 commit
-
Fix the gup benchmark flags to use the symbolic FOLL_WRITE, instead of a
hard-coded "1" value.Also, clean up the filtering of gup flags a little, by just doing it
once before issuing any of the get_user_pages*() calls. This makes it
harder to overlook, instead of having little "gup_flags & 1" phrases in
the function calls.Link: http://lkml.kernel.org/r/20200107224558.2362728-22-jhubbard@nvidia.com
Signed-off-by: John Hubbard
Reviewed-by: Ira Weiny
Cc: Alex Williamson
Cc: Aneesh Kumar K.V
Cc: Björn Töpel
Cc: Christoph Hellwig
Cc: Daniel Vetter
Cc: Dan Williams
Cc: Hans Verkuil
Cc: Jan Kara
Cc: Jason Gunthorpe
Cc: Jason Gunthorpe
Cc: Jens Axboe
Cc: Jerome Glisse
Cc: Jonathan Corbet
Cc: Kirill A. Shutemov
Cc: Leon Romanovsky
Cc: Mauro Carvalho Chehab
Cc: Mike Rapoport
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
05 Jan, 2020
1 commit
-
In the implementation of __gup_benchmark_ioctl() the allocated pages
should be released before returning in case of an invalid cmd. Release
pages via kvfree().[akpm@linux-foundation.org: rework code flow, return -EINVAL rather than -1]
Link: http://lkml.kernel.org/r/20191211174653.4102-1-navid.emamdoost@gmail.com
Fixes: 714a3a1ebafe ("mm/gup_benchmark.c: add additional pinning methods")
Signed-off-by: Navid Emamdoost
Reviewed-by: Andrew Morton
Reviewed-by: Ira Weiny
Reviewed-by: John Hubbard
Cc: Keith Busch
Cc: Kirill A. Shutemov
Cc: Dave Hansen
Cc: Dan Williams
Cc: David Hildenbrand
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
15 May, 2019
1 commit
-
Pach series "Add FOLL_LONGTERM to GUP fast and use it".
HFI1, qib, and mthca, use get_user_pages_fast() due to its performance
advantages. These pages can be held for a significant time. But
get_user_pages_fast() does not protect against mapping FS DAX pages.Introduce FOLL_LONGTERM and use this flag in get_user_pages_fast() which
retains the performance while also adding the FS DAX checks. XDP has also
shown interest in using this functionality.[1]In addition we change get_user_pages() to use the new FOLL_LONGTERM flag
and remove the specialized get_user_pages_longterm call.[1] https://lkml.org/lkml/2019/3/19/939
"longterm" is a relative thing and at this point is probably a misnomer.
This is really flagging a pin which is going to be given to hardware and
can't move. I've thought of a couple of alternative names but I think we
have to settle on if we are going to use FL_LAYOUT or something else to
solve the "longterm" problem. Then I think we can change the flag to a
better name.Secondly, it depends on how often you are registering memory. I have
spoken with some RDMA users who consider MR in the performance path...
For the overall application performance. I don't have the numbers as the
tests for HFI1 were done a long time ago. But there was a significant
advantage. Some of which is probably due to the fact that you don't have
to hold mmap_sem.Finally, architecturally I think it would be good for everyone to use
*_fast. There are patches submitted to the RDMA list which would allow
the use of *_fast (they reworking the use of mmap_sem) and as soon as they
are accepted I'll submit a patch to convert the RDMA core as well. Also
to this point others are looking to use *_fast.As an aside, Jasons pointed out in my previous submission that *_fast and
*_unlocked look very much the same. I agree and I think further cleanup
will be coming. But I'm focused on getting the final solution for DAX at
the moment.This patch (of 7):
This patch starts a series which aims to support FOLL_LONGTERM in
get_user_pages_fast(). Some callers who would like to do a longterm (user
controlled pin) of pages with the fast variant of GUP for performance
purposes.Rather than have a separate get_user_pages_longterm() call, introduce
FOLL_LONGTERM and change the longterm callers to use it.This patch does not change any functionality. In the short term
"longterm" or user controlled pins are unsafe for Filesystems and FS DAX
in particular has been blocked. However, callers of get_user_pages_fast()
were not "protected".FOLL_LONGTERM can _only_ be supported with get_user_pages[_fast]() as it
requires vmas to determine if DAX is in use.NOTE: In merging with the CMA changes we opt to change the
get_user_pages() call in check_and_migrate_cma_pages() to a call of
__get_user_pages_locked() on the newly migrated pages. This makes the
code read better in that we are calling __get_user_pages_locked() on the
pages before and after a potential migration.As a side affect some of the interfaces are cleaned up but this is not the
primary purpose of the series.In review[1] it was asked:
> This I don't get - if you do lock down long term mappings performance
> of the actual get_user_pages call shouldn't matter to start with.
>
> What do I miss?A couple of points.
First "longterm" is a relative thing and at this point is probably a
misnomer. This is really flagging a pin which is going to be given to
hardware and can't move. I've thought of a couple of alternative names
but I think we have to settle on if we are going to use FL_LAYOUT or
something else to solve the "longterm" problem. Then I think we can
change the flag to a better name.Second, It depends on how often you are registering memory. I have spoken
with some RDMA users who consider MR in the performance path... For the
overall application performance. I don't have the numbers as the tests
for HFI1 were done a long time ago. But there was a significant
advantage. Some of which is probably due to the fact that you don't have
to hold mmap_sem.Finally, architecturally I think it would be good for everyone to use
*_fast. There are patches submitted to the RDMA list which would allow
the use of *_fast (they reworking the use of mmap_sem) and as soon as they
are accepted I'll submit a patch to convert the RDMA core as well. Also
to this point others are looking to use *_fast.As an asside, Jasons pointed out in my previous submission that *_fast and
*_unlocked look very much the same. I agree and I think further cleanup
will be coming. But I'm focused on getting the final solution for DAX at
the moment.[1] https://lore.kernel.org/lkml/20190220180255.GA12020@iweiny-DESK2.sc.intel.com/T/#md6abad2569f3bf6c1f03686c8097ab6563e94965
[ira.weiny@intel.com: v3]
Link: http://lkml.kernel.org/r/20190328084422.29911-2-ira.weiny@intel.com
Link: http://lkml.kernel.org/r/20190328084422.29911-2-ira.weiny@intel.com
Link: http://lkml.kernel.org/r/20190317183438.2057-2-ira.weiny@intel.com
Signed-off-by: Ira Weiny
Reviewed-by: Andrew Morton
Cc: Aneesh Kumar K.V
Cc: Michal Hocko
Cc: John Hubbard
Cc: "Kirill A. Shutemov"
Cc: Peter Zijlstra
Cc: Jason Gunthorpe
Cc: Benjamin Herrenschmidt
Cc: Paul Mackerras
Cc: "David S. Miller"
Cc: Martin Schwidefsky
Cc: Heiko Carstens
Cc: Rich Felker
Cc: Yoshinori Sato
Cc: Thomas Gleixner
Cc: Ingo Molnar
Cc: Borislav Petkov
Cc: Ralf Baechle
Cc: James Hogan
Cc: Dan Williams
Cc: Mike Marshall
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
06 Mar, 2019
1 commit
-
When calling debugfs functions, there is no need to ever check the
return value. The function can work or not, but the code logic should
never do something different based on this.Link: http://lkml.kernel.org/r/20190122152151.16139-14-gregkh@linuxfoundation.org
Signed-off-by: Greg Kroah-Hartman
Cc: Michal Hocko
Cc: Vlastimil Babka
Cc: David Rientjes
Cc: Laura Abbott
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
31 Oct, 2018
1 commit
-
The concern here is that "gup->size" is a u64 and "nr_pages" is unsigned
long. On 32 bit systems we could trick the kernel into allocating fewer
pages than expected.Link: http://lkml.kernel.org/r/20181025061546.hnhkv33diogf2uis@kili.mountain
Fixes: 64c349f4ae78 ("mm: add infrastructure for get_user_pages_fast() benchmarking")
Signed-off-by: Dan Carpenter
Acked-by: Kirill A. Shutemov
Reviewed-by: Andrew Morton
Cc: Stephen Rothwell
Cc: Keith Busch
Cc: "Michael S. Tsirkin"
Cc: Kees Cook
Cc: YueHaibing
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
27 Oct, 2018
2 commits
-
Provide new gup benchmark ioctl commands to run different user page
pinning methods, get_user_pages_longterm() and get_user_pages(), in
addition to the existing get_user_pages_fast().Link: http://lkml.kernel.org/r/20181010195605.10689-2-keith.busch@intel.com
Signed-off-by: Keith Busch
Acked-by: Kirill A. Shutemov
Reviewed-by: Andrew Morton
Cc: Dave Hansen
Cc: Dan Williams
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds -
We'd like to measure time to unpin user pages, so this adds a second
benchmark timer on put_page, separate from get_page.Adding the field breaks this ioctl ABI, but should be okay since this an
in-tree kernel selftest.[akpm@linux-foundation.org: add expansion to struct gup_benchmark for future use]
Link: http://lkml.kernel.org/r/20181010195605.10689-1-keith.busch@intel.com
Signed-off-by: Keith Busch
Acked-by: Kirill A. Shutemov
Reviewed-by: Andrew Morton
Cc: Dave Hansen
Cc: Dan Williams
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
06 Oct, 2018
1 commit
-
get_user_pages_fast() will return negative value if no pages were pinned,
then be converted to a unsigned, which is compared to zero, giving the
wrong result.Link: http://lkml.kernel.org/r/20180921095015.26088-1-yuehaibing@huawei.com
Fixes: 09e35a4a1ca8 ("mm/gup_benchmark: handle gup failures")
Signed-off-by: YueHaibing
Reviewed-by: Andrew Morton
Cc: Michael S. Tsirkin
Signed-off-by: Andrew Morton
Signed-off-by: Greg Kroah-Hartman
13 Jun, 2018
1 commit
-
The kvzalloc() function has a 2-factor argument form, kvcalloc(). This
patch replaces cases of:kvzalloc(a * b, gfp)
with:
kvcalloc(a * b, gfp)as well as handling cases of:
kvzalloc(a * b * c, gfp)
with:
kvzalloc(array3_size(a, b, c), gfp)
as it's slightly less ugly than:
kvcalloc(array_size(a, b), c, gfp)
This does, however, attempt to ignore constant size factors like:
kvzalloc(4 * 1024, gfp)
though any constants defined via macros get caught up in the conversion.
Any factors with a sizeof() of "unsigned char", "char", and "u8" were
dropped, since they're redundant.The Coccinelle script used for this was:
// Fix redundant parens around sizeof().
@@
type TYPE;
expression THING, E;
@@(
kvzalloc(
- (sizeof(TYPE)) * E
+ sizeof(TYPE) * E
, ...)
|
kvzalloc(
- (sizeof(THING)) * E
+ sizeof(THING) * E
, ...)
)// Drop single-byte sizes and redundant parens.
@@
expression COUNT;
typedef u8;
typedef __u8;
@@(
kvzalloc(
- sizeof(u8) * (COUNT)
+ COUNT
, ...)
|
kvzalloc(
- sizeof(__u8) * (COUNT)
+ COUNT
, ...)
|
kvzalloc(
- sizeof(char) * (COUNT)
+ COUNT
, ...)
|
kvzalloc(
- sizeof(unsigned char) * (COUNT)
+ COUNT
, ...)
|
kvzalloc(
- sizeof(u8) * COUNT
+ COUNT
, ...)
|
kvzalloc(
- sizeof(__u8) * COUNT
+ COUNT
, ...)
|
kvzalloc(
- sizeof(char) * COUNT
+ COUNT
, ...)
|
kvzalloc(
- sizeof(unsigned char) * COUNT
+ COUNT
, ...)
)// 2-factor product with sizeof(type/expression) and identifier or constant.
@@
type TYPE;
expression THING;
identifier COUNT_ID;
constant COUNT_CONST;
@@(
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * (COUNT_ID)
+ COUNT_ID, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * COUNT_ID
+ COUNT_ID, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * (COUNT_CONST)
+ COUNT_CONST, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * COUNT_CONST
+ COUNT_CONST, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * (COUNT_ID)
+ COUNT_ID, sizeof(THING)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * COUNT_ID
+ COUNT_ID, sizeof(THING)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * (COUNT_CONST)
+ COUNT_CONST, sizeof(THING)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * COUNT_CONST
+ COUNT_CONST, sizeof(THING)
, ...)
)// 2-factor product, only identifiers.
@@
identifier SIZE, COUNT;
@@- kvzalloc
+ kvcalloc
(
- SIZE * COUNT
+ COUNT, SIZE
, ...)// 3-factor product with 1 sizeof(type) or sizeof(expression), with
// redundant parens removed.
@@
expression THING;
identifier STRIDE, COUNT;
type TYPE;
@@(
kvzalloc(
- sizeof(TYPE) * (COUNT) * (STRIDE)
+ array3_size(COUNT, STRIDE, sizeof(TYPE))
, ...)
|
kvzalloc(
- sizeof(TYPE) * (COUNT) * STRIDE
+ array3_size(COUNT, STRIDE, sizeof(TYPE))
, ...)
|
kvzalloc(
- sizeof(TYPE) * COUNT * (STRIDE)
+ array3_size(COUNT, STRIDE, sizeof(TYPE))
, ...)
|
kvzalloc(
- sizeof(TYPE) * COUNT * STRIDE
+ array3_size(COUNT, STRIDE, sizeof(TYPE))
, ...)
|
kvzalloc(
- sizeof(THING) * (COUNT) * (STRIDE)
+ array3_size(COUNT, STRIDE, sizeof(THING))
, ...)
|
kvzalloc(
- sizeof(THING) * (COUNT) * STRIDE
+ array3_size(COUNT, STRIDE, sizeof(THING))
, ...)
|
kvzalloc(
- sizeof(THING) * COUNT * (STRIDE)
+ array3_size(COUNT, STRIDE, sizeof(THING))
, ...)
|
kvzalloc(
- sizeof(THING) * COUNT * STRIDE
+ array3_size(COUNT, STRIDE, sizeof(THING))
, ...)
)// 3-factor product with 2 sizeof(variable), with redundant parens removed.
@@
expression THING1, THING2;
identifier COUNT;
type TYPE1, TYPE2;
@@(
kvzalloc(
- sizeof(TYPE1) * sizeof(TYPE2) * COUNT
+ array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
, ...)
|
kvzalloc(
- sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+ array3_size(COUNT, sizeof(TYPE1), sizeof(TYPE2))
, ...)
|
kvzalloc(
- sizeof(THING1) * sizeof(THING2) * COUNT
+ array3_size(COUNT, sizeof(THING1), sizeof(THING2))
, ...)
|
kvzalloc(
- sizeof(THING1) * sizeof(THING2) * (COUNT)
+ array3_size(COUNT, sizeof(THING1), sizeof(THING2))
, ...)
|
kvzalloc(
- sizeof(TYPE1) * sizeof(THING2) * COUNT
+ array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
, ...)
|
kvzalloc(
- sizeof(TYPE1) * sizeof(THING2) * (COUNT)
+ array3_size(COUNT, sizeof(TYPE1), sizeof(THING2))
, ...)
)// 3-factor product, only identifiers, with redundant parens removed.
@@
identifier STRIDE, SIZE, COUNT;
@@(
kvzalloc(
- (COUNT) * STRIDE * SIZE
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- COUNT * (STRIDE) * SIZE
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- COUNT * STRIDE * (SIZE)
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- (COUNT) * (STRIDE) * SIZE
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- COUNT * (STRIDE) * (SIZE)
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- (COUNT) * STRIDE * (SIZE)
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- (COUNT) * (STRIDE) * (SIZE)
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
|
kvzalloc(
- COUNT * STRIDE * SIZE
+ array3_size(COUNT, STRIDE, SIZE)
, ...)
)// Any remaining multi-factor products, first at least 3-factor products,
// when they're not all constants...
@@
expression E1, E2, E3;
constant C1, C2, C3;
@@(
kvzalloc(C1 * C2 * C3, ...)
|
kvzalloc(
- (E1) * E2 * E3
+ array3_size(E1, E2, E3)
, ...)
|
kvzalloc(
- (E1) * (E2) * E3
+ array3_size(E1, E2, E3)
, ...)
|
kvzalloc(
- (E1) * (E2) * (E3)
+ array3_size(E1, E2, E3)
, ...)
|
kvzalloc(
- E1 * E2 * E3
+ array3_size(E1, E2, E3)
, ...)
)// And then all remaining 2 factors products when they're not all constants,
// keeping sizeof() as the second factor argument.
@@
expression THING, E1, E2;
type TYPE;
constant C1, C2, C3;
@@(
kvzalloc(sizeof(THING) * C2, ...)
|
kvzalloc(sizeof(TYPE) * C2, ...)
|
kvzalloc(C1 * C2 * C3, ...)
|
kvzalloc(C1 * C2, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * (E2)
+ E2, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(TYPE) * E2
+ E2, sizeof(TYPE)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * (E2)
+ E2, sizeof(THING)
, ...)
|
- kvzalloc
+ kvcalloc
(
- sizeof(THING) * E2
+ E2, sizeof(THING)
, ...)
|
- kvzalloc
+ kvcalloc
(
- (E1) * E2
+ E1, E2
, ...)
|
- kvzalloc
+ kvcalloc
(
- (E1) * (E2)
+ E1, E2
, ...)
|
- kvzalloc
+ kvcalloc
(
- E1 * E2
+ E1, E2
, ...)
)Signed-off-by: Kees Cook
14 Apr, 2018
1 commit
-
Patch series "mm/get_user_pages_fast fixes, cleanups", v2.
Turns out get_user_pages_fast and __get_user_pages_fast return different
values on error when given a single page: __get_user_pages_fast returns
0. get_user_pages_fast returns either 0 or an error.Callers of get_user_pages_fast expect an error so fix it up to return an
error consistently.Stress the difference between get_user_pages_fast and
__get_user_pages_fast to make sure callers aren't confused.This patch (of 3):
__gup_benchmark_ioctl does not handle the case where get_user_pages_fast
fails:- a negative return code will cause a buffer overrun
- returning with partial success will cause use of uninitialized
memory.[akpm@linux-foundation.org: simplification]
Link: http://lkml.kernel.org/r/1522962072-182137-3-git-send-email-mst@redhat.com
Signed-off-by: Michael S. Tsirkin
Reviewed-by: Andrew Morton
Cc: Kirill A. Shutemov
Cc: Huang Ying
Cc: Jonathan Corbet
Cc: Peter Zijlstra
Cc: Thomas Gleixner
Cc: Thorsten Leemhuis
Cc:
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
18 Nov, 2017
1 commit
-
Performance of get_user_pages_fast() is critical for some workloads, but
it's tricky to test it directly.This patch provides /sys/kernel/debug/gup_benchmark that helps with
testing performance of it.See tools/testing/selftests/vm/gup_benchmark.c for userspace
counterpart.Link: http://lkml.kernel.org/r/20170908215603.9189-2-kirill.shutemov@linux.intel.com
Signed-off-by: Kirill A. Shutemov
Cc: Shuah Khan
Cc: Ingo Molnar
Cc: Thorsten Leemhuis
Cc: Jonathan Corbet
Cc: Huang Ying
Signed-off-by: Andrew Morton
Signed-off-by: Linus Torvalds
