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authorAndrea Arcangeli <aarcange@redhat.com>2021-06-28 19:36:40 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2021-06-29 10:53:48 -0700
commita458b76a4171f893efa7657dc079924580a8746a (patch)
treedfeef6225048660a4659fa8a996998d70fd7b714 /fs/proc
parent292648ac5cf16ec1fce33e29e0f9e35da7de63f7 (diff)
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.c2
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)