Commit eb8abb92 authored Nov 02, 2010 by Theodore Ts'o Committed by Linus Torvalds Nov 02, 2010

ext4: Remove useless spinlock in ext4_getattr()



Linus noted, and complained to me, that doing while lots of "git diff"'s
of kernel sources, these spinlocks were responsible for 27% of the
spinlock cost on his two-processor system as reported by perf.

Git was doing lots of parallel stats, and this was putting a lot of
pressure on ext4_getattr().  A spinlock to protect a single
memory-to-memory copy is pointless, so remove it.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 7fe19da4

fs/ext4/inode.c

+0 −2

Original line number	Diff line number	Diff line
		@@ -5410,9 +5410,7 @@ int ext4_getattr(struct vfsmount mnt, struct dentry dentry,
		* will return the blocks that include the delayed allocation
		* blocks for this file.
		*/
		spin_lock(&EXT4_I(inode)->i_block_reservation_lock);
		delalloc_blocks = EXT4_I(inode)->i_reserved_data_blocks;
		spin_unlock(&EXT4_I(inode)->i_block_reservation_lock);

		stat->blocks += (delalloc_blocks << inode->i_sb->s_blocksize_bits)>>9;
		return 0;

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