The patch titled
aio: bump i_count instead of using igrab
has been added to the -mm tree. Its filename is
aio-bump-i_count-instead-of-using-igrab.patch
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Subject: aio: bump i_count instead of using igrab
From: Chris Mason <chris.mason@xxxxxxxxxx>
The aio batching code is using igrab to get an extra reference on the
inode so it can safely batch. igrab will go ahead and take the global
inode spinlock, which can be a bottleneck on large machines doing lots of
AIO.
In this case, igrab isn't required because we already have a reference on
the file handle. It is safe to just bump the i_count directly on the
inode.
Benchmarking shows this patch brings IOP/s on tons of flash up by about
2.5X.
Signed-off-by: Chris Mason <chris.mason@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Reviewed-by: Jeff Moyer <jmoyer@xxxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Cc: Zach Brown <zach.brown@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/aio.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff -puN fs/aio.c~aio-bump-i_count-instead-of-using-igrab fs/aio.c
--- a/fs/aio.c~aio-bump-i_count-instead-of-using-igrab
+++ a/fs/aio.c
@@ -1543,7 +1543,20 @@ static void aio_batch_add(struct address
}
abe = mempool_alloc(abe_pool, GFP_KERNEL);
- BUG_ON(!igrab(mapping->host));
+
+ /*
+ * we should be using igrab here, but
+ * we don't want to hammer on the global
+ * inode spinlock just to take an extra
+ * reference on a file that we must already
+ * have a reference to.
+ *
+ * When we're called, we always have a reference
+ * on the file, so we must always have a reference
+ * on the inode, so igrab must always just
+ * bump the count and move on.
+ */
+ atomic_inc(&mapping->host->i_count);
abe->mapping = mapping;
hlist_add_head(&abe->list, &batch_hash[bucket]);
return;
_
Patches currently in -mm which might be from chris.mason@xxxxxxxxxx are
linux-next.patch
fs-btrfs-use-memdup_user.patch
fs-btrfs-use-err_cast.patch
gcc-46-btrfs-clean-up-unused-variables-bugs.patch
gcc-46-btrfs-clean-up-unused-variables-nonbugs.patch
btrfs-only-bug_on-when-the-errno-is-not-enoent.patch
fs-btrfs-inodec-eliminate-memory-leak.patch
writeback-remove-nonblocking-encountered_congestion-references.patch
aio-bump-i_count-instead-of-using-igrab.patch
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