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authorNicholas Piggin <npiggin@gmail.com>2016-12-25 06:00:30 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2016-12-25 22:54:48 +0300
commit62906027091f1d02de44041524f0769f60bb9cf3 (patch)
tree6444171af03e463bb0123a392d7b91a0ae6a1f40 /include/linux/pagemap.h
parent6326fec1122cde256bd2a8c63f2606e08e44ce1d (diff)
downloadlinux-62906027091f1d02de44041524f0769f60bb9cf3.tar.xz
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/pagemap.h')
-rw-r--r--include/linux/pagemap.h23
1 files changed, 11 insertions, 12 deletions
diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h
index f29f80f81dbf..324c8dbad1e1 100644
--- a/include/linux/pagemap.h
+++ b/include/linux/pagemap.h
@@ -486,22 +486,14 @@ static inline int lock_page_or_retry(struct page *page, struct mm_struct *mm,
* and for filesystems which need to wait on PG_private.
*/
extern void wait_on_page_bit(struct page *page, int bit_nr);
-
extern int wait_on_page_bit_killable(struct page *page, int bit_nr);
-extern int wait_on_page_bit_killable_timeout(struct page *page,
- int bit_nr, unsigned long timeout);
-
-static inline int wait_on_page_locked_killable(struct page *page)
-{
- if (!PageLocked(page))
- return 0;
- return wait_on_page_bit_killable(compound_head(page), PG_locked);
-}
+extern void wake_up_page_bit(struct page *page, int bit_nr);
-extern wait_queue_head_t *page_waitqueue(struct page *page);
static inline void wake_up_page(struct page *page, int bit)
{
- __wake_up_bit(page_waitqueue(page), &page->flags, bit);
+ if (!PageWaiters(page))
+ return;
+ wake_up_page_bit(page, bit);
}
/*
@@ -517,6 +509,13 @@ static inline void wait_on_page_locked(struct page *page)
wait_on_page_bit(compound_head(page), PG_locked);
}
+static inline int wait_on_page_locked_killable(struct page *page)
+{
+ if (!PageLocked(page))
+ return 0;
+ return wait_on_page_bit_killable(compound_head(page), PG_locked);
+}
+
/*
* Wait for a page to complete writeback
*/