Created attachment 411033 [details]
Description of problem: There is a limitation in the behind writes capability of the md driver. Particularly, when the counter goes over a certain limit, performance suffers. This patch exposes the counter and allows userspace to deal with the issue.
The patch has been accepted by the maintainer, Neil Brown, and is attached.
This request was evaluated by Red Hat Product Management for inclusion in a Red
Hat Enterprise Linux major release. Product Management has requested further
review of this request by Red Hat Engineering, for potential inclusion in a Red
Hat Enterprise Linux Major release. This request is not yet committed for
I've verified that Neil has accepted the patch, although he has not yet forwarded it on to Linus. However, the patch is simple enough that I'm not concerned with that at this point. That it is in Neil's git repo on his md-scratch branch is sufficient for me.
Patch(es) available on kernel-2.6.32-30.el6
Verified on RHEL6.0-20100922.1
# ls /sys/block/md0/md/bitmap
backlog can_clear chunksize location max_backlog_used metadata time_base
Red Hat Enterprise Linux 6.0 is now available and should resolve
the problem described in this bug report. This report is therefore being closed
with a resolution of CURRENTRELEASE. You may reopen this bug report if the
solution does not work for you.