On Fri, May 03, 2013 at 01:56:52PM -0400, Vivek Goyal wrote: > > Yeah, I think that's what *should* be happening but not what I'm > > seeing. I'm seeing ~15% penalty. > > What test are you running. I am running a simple dd with directIO and > I am not seeing any penalty. Combination of dd and a test program that I've been using for some while which can generate concurrent direct random IOs. Attaching the source code for the latter. > # set limit to 1000000 bytes/second both in parent and child cgroup > # dd if=/dev/vdb of=/dev/null iflag=direct > > I will capture blktrace and analyze it though to understand better > what's happening. Try using larger block size. It looks like dispatch windows being reset depending on timing is hurting the overall bandwidth. It becomes pronounced with larger IOs. Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
