On Fri, May 15, 2015 at 1:37 PM, Darrick J. Wong
[off-list ref] wrote:

On Fri, May 15, 2015 at 10:55:32AM -0700, Eric Wheeler wrote:

quoted

quoted

Going through various forum messages and bug reports (for Debian:
https://lists.debian.org/debian-kernel/2015/03/msg00060.html for Arch:
https://bugs.archlinux.org/task/38843 for some other distro:
https://groups.google.com/forum/#!msg/esos-users/NXp8tG7sVE8/QXZyPdZ2saIJ
) it looks like the bcache_writeback kernel thread, being in
uninterruptible sleep, keeps the load average at 1.0 (or maybe more)
always. Could you please confirm this ?

Try the attached patches that I've been collecting over the past year or
two. I do not believe they have been merged into mainline (BUT SOMEONE
NEEDS TO).

I am not sure that these address the load bug, but if the load is being
increased by a large amount of dmesg output caused by rcu traces, then the
patches will help.

I just put all five of them into a 4.0.3 kernel, but sadly they don't
fix the load average bug.  That said, they look like pretty reasonable
bugfixes to me.  Maybe someone should just send them to Linus, if the
maintainer hasn't otherwise objected?

I have put the patches here.
https://git.kernel.org/cgit/linux/kernel/git/mlin/linux.git/log/?h=bcache

I'm new to bcache code.
I'll read these patches and run some tests.

Ming