Kernel version: 4.4.0-62 Backing Devices: Segate Enterprise 7.2K rpm 2TB SAS (ST2000NX0433) Cache Device: Intel DC P3700 NVMe 1.6TB bcache cache mode: writeback # make-bcache --block 4k --bucket 2M -B /dev/sdb -C /dev/nvme0n1p2 Created backing and cache devices with above command. I was expecting very high number of iops with and without fsync option of fio. fio command without fsync: # fio -filename=/dev/bcache0 -direct=1 -ioengine=libaio -rw=randwrite -bs=4k -name=mytest -iodepth=1 -runtime=30 -time_based iops : 35k fio command with fsync: fio -filename=/dev/bcache0 -direct=1 -ioengine=libaio -rw=randwrite -bs=4k -name=mytest -iodepth=1 -runtime=30 -time_based -fsync=1 iops: 8.1k Attempted following combinations and saw same results: 1. block size 512,4k bucket, 512k, 2M, 4M for bcache devices 2. fio -rw option of write also showed similar results. 3. bcache writeback_percent 10 or 50; sequential_cutoff: 64M ; read_ahead_kb: 4k 4. Captured blktrace for a single io and that didn't show anything interes I'm quite surprised by the drop in iops with fsync turned on. Is this expected or am I missing some basic setting? Appreciate any help !. Thanks, Shiva -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
