Using tasklets for disk verification can reduce IO latency. When there are accelerated hash instructions it is often better to compute the hash immediately using a tasklet rather than deferring verification to a work-queue. This reduces time spent waiting to schedule work-queue jobs, but requires spending slightly more time in interrupt context. A tasklet can only be used for verification if all the required hashes are already in the dm-bufio cache. If verification cannot be done in a tasklet, we fallback the existing work-queue implementation. To allow tasklets to query the dm-bufio cache, the dm-bufio code must not sleep. This patchset adds a flag to dm-bufio that disallows sleeping. The following shows a speed comparison of random reads on a dm-verity device. The dm-verity device uses a 1G ramdisk for data and a 1G ramdisk for hashes. One test was run using tasklets and one test was run using the existing work-queue solution. Both tests were run when the dm-bufio cache was hot. The tasklet implementation performs significantly better since there is no time waiting for work-queue jobs to be scheduled. # /data/fio /data/tasklet.fio | grep READ READ: bw=181MiB/s (190MB/s), 181MiB/s-181MiB/s (190MB/s-190MB/s), io=512MiB (537MB), run=2827-2827msec # /data/fio /data/workqueue.fio | grep READ READ: bw=23.6MiB/s (24.8MB/s), 23.6MiB/s-23.6MiB/s (24.8MB/s-24.8MB/s), io=512MiB (537MB), run=21688-21688msec Nathan Huckleberry (3): dm-bufio: Add flags for dm_bufio_client_create dm-bufio: Add DM_BUFIO_GET_CANT_SLEEP dm-verity: Add try_verify_in_tasklet drivers/md/dm-bufio.c | 29 +++++-- drivers/md/dm-ebs-target.c | 3 +- drivers/md/dm-integrity.c | 2 +- drivers/md/dm-snap-persistent.c | 2 +- drivers/md/dm-verity-fec.c | 4 +- drivers/md/dm-verity-target.c | 87 ++++++++++++++++--- drivers/md/dm-verity.h | 5 ++ drivers/md/persistent-data/dm-block-manager.c | 3 +- include/linux/dm-bufio.h | 8 +- 9 files changed, 119 insertions(+), 24 deletions(-) -- 2.37.1.359.gd136c6c3e2-goog -- dm-devel mailing list dm-devel@xxxxxxxxxx https://listman.redhat.com/mailman/listinfo/dm-devel
