Btrfs: reduce lock contention on extent buffer locks

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The extent buffers have a refs_lock which we use to make coordinate freeing
the extent buffer with operations on the radix tree.  On tree roots and
other extent buffers that very cache hot, this can be highly contended.

These are also the extent buffers that are basically pinned in memory.
This commit adds code to cmpxchg our way through the ref modifications,
and as long as the result of the reference change is still pinned in
ram, we skip the expensive spinlock.

Signed-off-by: Chris Mason <chris.mason@fusionio.com>

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Chris Mason 2013-01-29 17:49:37 -05:00

parent 8de972b4fa

commit 242e18c7c1

1 changed files with 16 additions and 0 deletions

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fs/btrfs/extent_io.c

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