On Fri, Aug 02, 2013 at 09:23:44AM -0400, Mike Snitzer wrote: > Yes, it is surprising. Curious to know if the promotions aren't > happening due to the IO scheduler somehow merging all your random small > IO. We don't yet have a descrete counter to show the number of > migrations that were skipped due to sequential_threshold but that is > something we can add. > > But you can effectively disable the sequential_threshold by setting it > really high, e.g.: > > dmsetup message cache 0 sequential_threshold 16384 I tried this, and it still doesn't appear to promote anything at all: cache: 0 23440891904 cache 913/8192 0 7021239 0 2049048 0 0 0 0 0 2 migration_threshold 2048 4 random_threshold 8 sequential_threshold 16384 It's only been running for a few minutes, though. FWIW, earlier I ran it on only one single partition, and then it worked. So it's not like my kernel is completely broken, at least. > Please write a file that is smaller than your specified > sequential_threshold, and then read it numerous times via direct IO, > e.g.: > > dd if=<your file> of=/dev/null iflag=direct bs=16K I did, with a 16 kB file (that should certainly be small enough, right?), executing the dd command 10000 times. Still nothing cached. /* Steinar */ -- Homepage: http://www.sesse.net/ -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
