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Btrfs: do not async metadata csumming in certain situations

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There are a coule scenarios where farming metadata csumming off to an async
thread doesn't help.  The first is if our processor supports crc32c, in
which case the csumming will be fast and so the overhead of the async model
is not worth the cost.  The other case is for our tree log.  We will be
making that stuff dirty and writing it out and waiting for it immediately.
Even with software crc32c this gives me a ~15% increase in speed with O_SYNC
workloads.  Thanks,

Signed-off-by: Josef Bacik <jbacik@fusionio.com>
This commit is contained in:
Josef Bacik 2012-09-25 14:25:58 -04:00 • committed by Chris Mason
parent 221b831835
commit de0022b9da
3 changed files with 35 additions and 2 deletions
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1
fs/btrfs/extent_io.h
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@ -27,6 +27,7 @@
* type for this bio
*/
#define EXTENT_BIO_COMPRESSED 1
#define EXTENT_BIO_TREE_LOG 2
#define EXTENT_BIO_FLAG_SHIFT 16
/* these are bit numbers for test/set bit */