[dm-devel] Performance impact of CONFIG_SCHED_MC? direct-io test case

[Dominik Brodowski]

How large is the performance impact of CONFIG_SCHED_MC -- for which there
is a warning that it comes "at a cost of slightly increased overhead in
some places."? Well, for the test workload I've been working with lately,

dd if=<device> of=/dev/zero bs=8k count=100000 iflag=direct

where <device> is a dm-crypted LVM volume consisting of several
partitions on a notebook pata harddisk, and all this runs on a Core2 Duo,
I get a ~ 10 % performance reduction if CONFIG_SCHED_MC is enabled.

Combined with the CONFIG_DEBUG performance reduction mentioned in the other
message, all of the reduction from 28 MB/s to 18 MB/s is explained for.

Best,
	Dominik

PS: Ingo: you got both mingo at elte.hu and mingo at redhat.com in MAINTAINERS,
I suppose both are valid?