tree 69d0df75fe55f7c4e9b2f1a1651478e37a3d2920
parent 5b050f04c8ce911c5b6831305a24d70eab95e732
author Chris Mason <chris.mason@oracle.com> 1226588376 -0500
committer Chris Mason <chris.mason@oracle.com> 1226588376 -0500

Btrfs: Improve metadata read latencies

This fixes latency problems on metadata reads by making sure they
don't go through the async submit queue, and by tuning down the amount
of readahead done during btree searches.

Also, the btrfs bdi congestion function is tuned to ignore the
number of pending async bios and checksums pending.  There is additional
code that throttles new async bios now and the congestion function
doesn't need to worry about it anymore.

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