diff options
| author | Andrea Arcangeli <aarcange@redhat.com> | 2021-06-29 04:36:40 +0200 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2021-06-29 19:53:48 +0200 |
| commit | a458b76a4171f893efa7657dc079924580a8746a (patch) | |
| tree | dfeef6225048660a4659fa8a996998d70fd7b714 /fs/proc | |
| parent | mm: gup: allow FOLL_PIN to scale in SMP (diff) | |
| download | linux-a458b76a4171f893efa7657dc079924580a8746a.tar.xz linux-a458b76a4171f893efa7657dc079924580a8746a.zip | |
mm: gup: pack has_pinned in MMF_HAS_PINNED
has_pinned 32bit can be packed in the MMF_HAS_PINNED bit as a noop
cleanup.
Any atomic_inc/dec to the mm cacheline shared by all threads in pin-fast
would reintroduce a loss of SMP scalability to pin-fast, so there's no
future potential usefulness to keep an atomic in the mm for this.
set_bit(MMF_HAS_PINNED) will be theoretically a bit slower than WRITE_ONCE
(atomic_set is equivalent to WRITE_ONCE), but the set_bit (just like
atomic_set after this commit) has to be still issued only once per "mm",
so the difference between the two will be lost in the noise.
will-it-scale "mmap2" shows no change in performance with enterprise
config as expected.
will-it-scale "pin_fast" retains the > 4000% SMP scalability performance
improvement against upstream as expected.
This is a noop as far as overall performance and SMP scalability are
concerned.
[peterx@redhat.com: pack has_pinned in MMF_HAS_PINNED]
Link: https://lkml.kernel.org/r/YJqWESqyxa8OZA+2@t490s
[akpm@linux-foundation.org: coding style fixes]
[peterx@redhat.com: fix build for task_mmu.c, introduce mm_set_has_pinned_flag, fix comments]
Link: https://lkml.kernel.org/r/20210507150553.208763-4-peterx@redhat.com
Signed-off-by: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: John Hubbard <jhubbard@nvidia.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Jan Kara <jack@suse.cz>
Cc: Jann Horn <jannh@google.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Kirill Shutemov <kirill@shutemov.name>
Cc: Kirill Tkhai <ktkhai@virtuozzo.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'fs/proc')
| -rw-r--r-- | fs/proc/task_mmu.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c index fc9784544b24..66965ad88d8b 100644 --- a/fs/proc/task_mmu.c +++ b/fs/proc/task_mmu.c @@ -1047,7 +1047,7 @@ static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr, return false; if (!is_cow_mapping(vma->vm_flags)) return false; - if (likely(!atomic_read(&vma->vm_mm->has_pinned))) + if (likely(!test_bit(MMF_HAS_PINNED, &vma->vm_mm->flags))) return false; page = vm_normal_page(vma, addr, pte); if (!page) |