Hi all, I have installed Linux kernel 3.9.2 in my Fedora 18. When I ran FIO in bcache write-through mode, the performance was good, but running a similar test in bcache write-back mode, I got very poor performance. Did I miss any options when setting the write-back mode? Environment =========== 500G backing store at /dev/sdb1 150G SSD at /dev/sdc1 Write-through mode ================== make-bcache -B /dev/sdb1 -C /dev/sdc1 echo /dev/sdb1 > /sys/fs/bcache/register echo /dev/sdc1 > /sys/fs/bcache/register mkfs.ext4 /dev/bcache0 mount /dev/bcache0 /mnt/bcache Running FIO with random, 100% read, iosize=4096, queue depth=16 the result is approx. 65k IOPS Write-backe mode (setup is almost the same as write-through except the extra step at the end "echo writeback ...") ================ make-bcache -B /dev/sdb1 -C /dev/sdc1 echo /dev/sdb1 > /sys/fs/bcache/register echo /dev/sdc1 > /sys/fs/bcache/register mkfs.ext4 /dev/bcache0 mount /dev/bcache0 /mnt/bcache echo writeback > /sys/block/bcache0/bcache/cache_mode Running FIO with random, 100% read, iosize=4096, queue depth=16 the result is approx. 12k IOPS Running FIO with random, 80% read 20% write, iosize=4096, queue depth=16 the result is approx. 2k IOPS Thanks, Patrick -- 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
