Hello everyone. I'm trying to get my bcache setup running, but having almost all my traffic bypassing the cache. Here are some stats that I have: root@midnight:~# cat /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/stats_total/bypassed 2.8G root@midnight:~# cat /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/stats_total/cache_bypass_misses 247956 root@midnight:~# cat /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/stats_total/cache_bypass_hits 5597 root@midnight:~# cat /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/stats_total/cache_hits 233 root@midnight:~# cat /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/stats_total/cache_misses 243 And now for my machine setup. Running ubuntu 18.04 LTS with 5.0.0-31-lowlatency kernel. Cache device is a partition on NVMe PCI-e SSD with 4k logical and physical sector size. Backing device is LVM logical volume on a 3-drive MD RAID-0 with 64K stripe size, so it's optimal IO is 192K. I have aligned backing-dev data offset with make-bcache -B -o 15360 --writeback /dev/vm-vg/lvcachedvm-bdev I have tried all recommendations for routing traffic to SSD: echo 0 > /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/congested_read_threshold_us echo 0 > /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/congested_write_threshold_us echo 0 > /sys/fs/bcache/9820f407-457a-46e3-abc0-f2214d39b64c/bdev0/sequential_cutoff But I still get almost all traffic going to cache_bypass_misse. BTW, what does this stat mean? I don't get it from the in-kernel manual Any help?.. Thank you. Best regards, Sergey E. Kolesnikov
