Commit e1cb4f56 authored by Kent Overstreet's avatar Kent Overstreet
Browse files

bcachefs: Bias reads more in favor of faster device 



Per reports of performance issues on mixed multi device filesystems
where we're issuing too much IO to the spinning rust - tweak this
algorithm.

Signed-off-by: default avatarKent Overstreet <kent.overstreet@linux.dev>
parent f4d67f6d

fs/bcachefs/extents.c

+8 −0
Original line number Diff line number Diff line
@@ -89,6 +89,14 @@ static inline bool ptr_better(struct bch_fs *c, 
		u64 l1 = dev_latency(c, p1.ptr.dev);

		u64 l2 = dev_latency(c, p2.ptr.dev);



		/*

		 * Square the latencies, to bias more in favor of the faster

		 * device - we never want to stop issuing reads to the slower

		 * device altogether, so that we can update our latency numbers:

		 */

		l1 *= l1;

		l2 *= l2;



		/* Pick at random, biased in favor of the faster device: */



		return bch2_rand_range(l1 + l2) > l1;