btrfs: calculate discard delay based on number of extents

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An earlier patch keeps track of discardable_extents. These are
undiscarded extents managed by the free space cache. Here, we will use
this to dynamically calculate the discard delay interval.

There are 3 rate to consider. The first is the target convergence rate,
the rate to discard all discardable_extents over the
BTRFS_DISCARD_TARGET_MSEC time frame. This is clamped by the lower
limit, the iops limit or BTRFS_DISCARD_MIN_DELAY (1ms), and the upper
limit, BTRFS_DISCARD_MAX_DELAY (1s). We reevaluate this delay every
transaction commit.

Reviewed-by: Josef Bacik <josef@toxicpanda.com>
Signed-off-by: Dennis Zhou <dennis@kernel.org>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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Dennis Zhou 2020-01-02 16:26:35 -05:00 • committed by David Sterba

parent 5dc7c10b87

commit a230930084

5 changed files with 88 additions and 5 deletions

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2

fs/btrfs/ctree.h

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55

fs/btrfs/discard.c

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1

fs/btrfs/discard.h

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4

fs/btrfs/extent-tree.c

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31

fs/btrfs/sysfs.c

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