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From: Josef Bacik <jbacik@fb.com>
To: <viro@ZenIV.linux.org.uk>, <linux-fsdevel@vger.kernel.org>,
	<david@fromorbit.com>, <jack@suse.cz>,
	<linux-kernel@vger.kernel.org>
Subject: [PATCH] inode: add hlist_fake to avoid the inode hash lock in evict V2
Date: Thu, 12 Mar 2015 08:20:23 -0400	[thread overview]
Message-ID: <1426162823-31760-1-git-send-email-jbacik@fb.com> (raw)
In-Reply-To: <20150312095206.GM29656@ZenIV.linux.org.uk>

Some filesystems don't use the VFS inode hash and fake the fact they
are hashed so that all the writeback code works correctly. However,
this means the evict() path still tries to remove the inode from the
hash, meaning that the inode_hash_lock() needs to be taken
unnecessarily. Hence under certain workloads the inode_hash_lock can
be contended even if the inode is never actually hashed.

To avoid this add hlist_fake to test if the inode isn't actually
hashed to avoid taking the hash lock on inodes that have never been
hashed.  Based on Dave Chinner's

inode: add IOP_NOTHASHED to avoid inode hash lock in evict

basd on Al's suggestions.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fb.com>
---
V1->V2: Argh sorry, forgot to reset the author, my bad.

 include/linux/fs.h   | 2 +-
 include/linux/list.h | 5 +++++
 2 files changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/fs.h b/include/linux/fs.h
index b4d71b5..31da757 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2528,7 +2528,7 @@ static inline void insert_inode_hash(struct inode *inode)
 extern void __remove_inode_hash(struct inode *);
 static inline void remove_inode_hash(struct inode *inode)
 {
-	if (!inode_unhashed(inode))
+	if (!inode_unhashed(inode) && !hlist_fake(&inode->i_hash))
 		__remove_inode_hash(inode);
 }
 
diff --git a/include/linux/list.h b/include/linux/list.h
index feb773c..3e3e64a 100644
--- a/include/linux/list.h
+++ b/include/linux/list.h
@@ -672,6 +672,11 @@ static inline void hlist_add_fake(struct hlist_node *n)
 	n->pprev = &n->next;
 }
 
+static inline bool hlist_fake(struct hlist_node *h)
+{
+	return h->pprev == &h->next;
+}
+
 /*
  * Move a list from one list head to another. Fixup the pprev
  * reference of the first entry if it exists.
-- 
1.9.3


  parent reply	other threads:[~2015-03-12 12:20 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-03-10 19:45 [PATCH 0/9] Sync and VFS scalability improvements Josef Bacik
2015-03-10 19:45 ` [PATCH 1/9] writeback: plug writeback at a high level Josef Bacik
2015-03-10 19:45 ` [PATCH 2/9] inode: add IOP_NOTHASHED to avoid inode hash lock in evict Josef Bacik
2015-03-12  9:52   ` Al Viro
2015-03-12 12:18     ` [PATCH] inode: add hlist_fake to avoid the " Josef Bacik
2015-03-12 12:20     ` Josef Bacik [this message]
2015-03-14  7:00       ` [PATCH] inode: add hlist_fake to avoid the inode hash lock in evict V2 Jan Kara
2015-03-12 12:24     ` [PATCH 2/9] inode: add IOP_NOTHASHED to avoid inode hash lock in evict Josef Bacik
2015-03-10 19:45 ` [PATCH 3/9] inode: convert inode_sb_list_lock to per-sb Josef Bacik
2015-03-10 19:45 ` [PATCH 4/9] sync: serialise per-superblock sync operations Josef Bacik
2015-03-10 19:45 ` [PATCH 5/9] inode: rename i_wb_list to i_io_list Josef Bacik
2015-03-10 19:45 ` [PATCH 6/9] bdi: add a new writeback list for sync Josef Bacik
2015-03-16 10:14   ` Jan Kara
2015-03-10 19:45 ` [PATCH 7/9] writeback: periodically trim the writeback list Josef Bacik
2015-03-16 10:16   ` Jan Kara
2015-03-16 11:43     ` Jan Kara
2015-03-10 19:45 ` [PATCH 8/9] inode: convert per-sb inode list to a list_lru Josef Bacik
2015-03-16 12:27   ` Jan Kara
2015-03-16 15:34     ` Josef Bacik
2015-03-16 15:48       ` Jan Kara
2015-03-10 19:45 ` [PATCH 9/9] inode: don't softlockup when evicting inodes Josef Bacik
2015-03-16 12:31   ` Jan Kara
2015-03-16 11:39 ` [PATCH 0/9] Sync and VFS scalability improvements Jan Kara
2015-03-25 11:18 ` Mel Gorman

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