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author | Nicholas Piggin <npiggin@gmail.com> | 2016-12-25 13:00:30 +1000 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-12-25 11:54:48 -0800 |
commit | 62906027091f1d02de44041524f0769f60bb9cf3 (patch) | |
tree | 6444171af03e463bb0123a392d7b91a0ae6a1f40 /include/linux/mm.h | |
parent | 6326fec1122cde256bd2a8c63f2606e08e44ce1d (diff) | |
download | linux-stable-62906027091f1d02de44041524f0769f60bb9cf3.tar.gz linux-stable-62906027091f1d02de44041524f0769f60bb9cf3.tar.bz2 linux-stable-62906027091f1d02de44041524f0769f60bb9cf3.zip |
mm: add PageWaiters indicating tasks are waiting for a page bit
Add a new page flag, PageWaiters, to indicate the page waitqueue has
tasks waiting. This can be tested rather than testing waitqueue_active
which requires another cacheline load.
This bit is always set when the page has tasks on page_waitqueue(page),
and is set and cleared under the waitqueue lock. It may be set when
there are no tasks on the waitqueue, which will cause a harmless extra
wakeup check that will clears the bit.
The generic bit-waitqueue infrastructure is no longer used for pages.
Instead, waitqueues are used directly with a custom key type. The
generic code was not flexible enough to have PageWaiters manipulation
under the waitqueue lock (which simplifies concurrency).
This improves the performance of page lock intensive microbenchmarks by
2-3%.
Putting two bits in the same word opens the opportunity to remove the
memory barrier between clearing the lock bit and testing the waiters
bit, after some work on the arch primitives (e.g., ensuring memory
operand widths match and cover both bits).
Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Bob Peterson <rpeterso@redhat.com>
Cc: Steven Whitehouse <swhiteho@redhat.com>
Cc: Andrew Lutomirski <luto@kernel.org>
Cc: Andreas Gruenbacher <agruenba@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mel Gorman <mgorman@techsingularity.net>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/mm.h')
-rw-r--r-- | include/linux/mm.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/mm.h b/include/linux/mm.h index 4424784ac374..fe6b4036664a 100644 --- a/include/linux/mm.h +++ b/include/linux/mm.h @@ -1758,6 +1758,8 @@ static inline spinlock_t *pmd_lock(struct mm_struct *mm, pmd_t *pmd) return ptl; } +extern void __init pagecache_init(void); + extern void free_area_init(unsigned long * zones_size); extern void free_area_init_node(int nid, unsigned long * zones_size, unsigned long zone_start_pfn, unsigned long *zholes_size); |