Btrfs: don't read leaf blocks containing only checksums during truncate

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Checksum items take up a significant portion of the metadata for large files.
It is possible to avoid reading them during truncates by checking the keys in
the higher level nodes.

If a given leaf is followed by another leaf where the lowest key is a checksum
item from the same file, we know we can safely delete the leaf without
reading it.

For a 32GB file on a 6 drive raid0 array, Btrfs needs 8s to delete
the file with a cold cache.  It is read bound during the run.

With this change, Btrfs is able to delete the file in 0.5s

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

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This commit is contained in:

Chris Mason 2008-10-01 19:05:46 -04:00

parent cf74982385

commit 323ac95bce

3 changed files with 193 additions and 32 deletions

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69

fs/btrfs/ctree.c

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4

fs/btrfs/ctree.h

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152

fs/btrfs/inode.c

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