btrfs: avoid useless rbtree iterations when attempting to merge extent map

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When trying to merge an extent map that was just inserted or unpinned, we
will try to merge it with any adjacent extent map that is suitable.

However we will only check if our extent map is mergeable after searching
for the previous and next extent maps in the rbtree, meaning that we are
doing unnecessary calls to rb_prev() and rb_next() in case our extent map
is not mergeable (it's compressed, in the list of modifed extents, being
logged or pinned), wasting CPU time chasing rbtree pointers and pulling
in unnecessary cache lines.

So change the logic to check first if an extent map is mergeable before
searching for the next and previous extent maps in the rbtree.

Signed-off-by: Filipe Manana <fdmanana@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

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Filipe Manana 2023-12-04 16:20:30 +00:00 • committed by David Sterba

parent 00deaf04df

commit 1a9fb16c60

1 changed files with 21 additions and 17 deletions

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fs/btrfs/extent_map.c

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