Hi Kent, this is exactly the documentation I had followed to try to track the bad performance issues I was experiencing. Redoing a whole run, trying to force everything into writeback mode, by disabling both the sequential bypass echo 0 > /sys/block/bcache0/bcache/sequential_cutoff and the congested thresholds echo 0 > /sys/fs/bcache/<set>/congested_read_threshold_us, echo 0 > /sys/fs/bcache/<set>/congested_write_threshold_us I am obtaining the following figures, on a cached fs: seq-read: iops=12188 rand-read: iops=7392 seq-write: iops=430 rand-write: iops=454 I must be missing something, and I would really appreciate any help on the matter. Thanks in advance, Leslie. On Mon, Apr 29, 2013 at 7:52 PM, Kent Overstreet <kent.overstreet@xxxxxxxxx> wrote: > There's documentation for exactly this stuff, linked off the main page > of the wiki: > > http://atlas.evilpiepirate.org/git/linux-bcache.git/tree/Documentation/bcache.txt?h=bcache-dev#n126 > > On Mon, Apr 29, 2013 at 8:43 AM, Leslie Basmid <leslie.basmid@xxxxxxxxx> wrote: >> Hi all, >> >> I have chosen to install bcache using the bcache-for-upstream branch >> (recompiled this morning for the latest patches). Even though >> everything is running smoothly, I am surprised by the very poor >> performance I'm obtaining from my setup. >> >> 1. Everything is setup on my laptop which has a 500GB HD (sda) and a >> 16 GB SSD (sdb). >> 2. I have setup an LVM above bcache, and /dev/sda4 is the only cache >> partition. The whole thing was setup with: >> >> make-bcache -B /dev/sda4 -C /dev/sdb >> >> the LVM is "inside" /dev/sda4 >> 3. I am using fio as a benchmark, have setup writeback >> # cat /sys/block/bcache0/bcache/writeback_running >> 1 >> and I think I have followed every hints I could found about performance tuning. >> Yet, when running the ssd fio test suite on a file on partition that >> is not "cached", I am obtaining the following figures: >> seq-read: iops=29156 >> rand-read: iops=291 >> seq-write: iops=22355 >> rand-write: iops=260 >> >> Running it on a cached file system I'm obtaining: >> seq-read: iops=22196 >> rand-read: iops=330 >> seq-write: iops=15864 >> rand-write: iops=387 >> >> What am I missing ? >> The benchmark parameters are: >> bs=4k >> ioengine=libaio >> iodepth=64 >> size=1g >> direct=1 >> >> Thanks in advance for your answers, >> Leslie. >> -- >> 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 -- 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
