From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gabriel de Perthuis Subject: Re: Very poor performances with the bcache-for-upstream branch Date: Thu, 2 May 2013 05:50:54 +0000 (UTC) Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Return-path: Sender: linux-bcache-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: linux-bcache-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-bcache@vger.kernel.org > 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 ? Outside of the make-bcache, none of the commands you give in the thread prove that the cache is assembled (it's actually possible to have writeback_running = 1 with a detached bdev, though that's a bug in my opinion). What does `ls -d /sys/fs/bcache/*/bdev*` show?