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authorNick Piggin <nickpiggin@yahoo.com.au>2006-03-25 03:07:09 -0800
committerLinus Torvalds <torvalds@g5.osdl.org>2006-03-25 08:22:53 -0800
commitc32ccd87bfd1414b0aabfcd8dbc7539ad23bcbaa (patch)
tree612dc637976cbe36e8b72924a1f7bd76e75463fd /include/linux/dcache.h
parentbf36b9011e3c5b2739f9da2f6de8a6fa3edded32 (diff)
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[PATCH] inotify: lock avoidance with parent watch status in dentry
Previous inotify work avoidance is good when inotify is completely unused, but it breaks down if even a single watch is in place anywhere in the system. Robin Holt notices that udev is one such culprit - it slows down a 512-thread application on a 512 CPU system from 6 seconds to 22 minutes. Solve this by adding a flag in the dentry that tells inotify whether or not its parent inode has a watch on it. Event queueing to parent will skip taking locks if this flag is cleared. Setting and clearing of this flag on all child dentries versus event delivery: this is no in terms of race cases, and that was shown to be equivalent to always performing the check. The essential behaviour is that activity occuring _after_ a watch has been added and _before_ it has been removed, will generate events. Signed-off-by: Nick Piggin <npiggin@suse.de> Cc: Robert Love <rml@novell.com> Cc: John McCutchan <ttb@tentacle.dhs.org> Signed-off-by: Andrew Morton <akpm@osdl.org> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Diffstat (limited to 'include/linux/dcache.h')
-rw-r--r--include/linux/dcache.h2
1 files changed, 2 insertions, 0 deletions
diff --git a/include/linux/dcache.h b/include/linux/dcache.h
index 4361f3789975..d10bd30c337e 100644
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -162,6 +162,8 @@ d_iput: no no no yes
#define DCACHE_REFERENCED 0x0008 /* Recently used, don't discard. */
#define DCACHE_UNHASHED 0x0010
+#define DCACHE_INOTIFY_PARENT_WATCHED 0x0020 /* Parent inode is watched */
+
extern spinlock_t dcache_lock;
/**