Messages in this thread | | | Date | Tue, 24 Aug 2004 22:29:55 +0200 | From | Jens Axboe <> | Subject | Re: [PATCH] Speed up the cdrw packet writing driver |
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On Mon, Aug 23 2004, Peter Osterlund wrote: > Jens Axboe <axboe@suse.de> writes: > > > On Sat, Aug 14 2004, Peter Osterlund wrote: > > > Hi! > > > > > > This patch replaces the pd->bio_queue linked list with an rbtree. The > > > list can get very long (>200000 entries on a 1GB machine), so keeping > > > it sorted with a naive algorithm is far too expensive. > > > > It looks like you are assuming that bio->bi_sector is unique which isn't > > necessarily true. In that respect, list -> rbtree conversion isn't > > trivial (or, at least it requires extra code to handle this). > > I don't think that is assumed anywhere. > > The pkt_rbtree_find() function returns the first node with a sector > number >= s, even if there are multiple bios with bi_sector == s. Note > that the code branches to the left if s == tmp->bio->bi_sector. > > The pkt_rbtree_insert() function is careful to insert a bio after any > already existing bios with the same sector number. Note that it > branches to the right if s == tmp->bio->bi_sector. > > The tree rotations done internally in rbtree.c also can't mess things > up, because tree rotations don't change the inorder traversal order of > a tree.
You are right, the code looks fine indeed. The bigger problem is probably that a faster data structure is needed at all, having hundreds of thousands bio's pending for a packet writing device is not nice at all.
-- Jens Axboe
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