On Tue, Dec 20, 2011 at 05:14:18PM -0800, Frank Rowand wrote: [...] > >>> Hm, assuming that metadata is no longer an issue, why do you think avoiding > >>> cgroups would be a good idea? > >>> > >> > >> It's helpful for certain end users, particularly those in the embedded > >> world, to be able to disable as many config options as possible to reduce > >> the size of kernel image as much as possible, so they'll want a minimal > >> amount of kernel functionality that allows such notifications. Keep in > >> mind that CONFIG_CGROUP_MEM_RES_CTLR is not enabled by default because of > >> this (enabling it, CONFIG_RESOURCE_COUNTERS, and CONFIG_CGROUPS increases > >> the size of the kernel text by ~1%), > > > > So for 2MB kernel that's about 20KB of an additional text... This seems > > affordable, especially as a trade-off for the things that cgroups may > > provide. > > A comment from http://lkml.indiana.edu/hypermail/linux/kernel/1102.1/00412.html: > > "I care about 5K. (But honestly, I don't actively hunt stuff less than > 10K in size, because there's too many of them to chase, currently)." I have just tried to turn off CGROUPS on my qemu test kernels: $ diff -u cgroups no_cgroups text data bss dec hex filename -3869810 465976 565248 4901034 4ac8aa vmlinux +3806374 460544 540672 4807590 495ba6 vmlinux So, that's actually ~60KB. Which is serious. memcontrol.o text size is about 23KB. And my cgroups setup was just this: $ cat .config | grep CGRO CONFIG_CGROUPS=y # CONFIG_CGROUP_DEBUG is not set # CONFIG_CGROUP_FREEZER is not set # CONFIG_CGROUP_DEVICE is not set # CONFIG_CGROUP_CPUACCT is not set CONFIG_CGROUP_MEM_RES_CTLR=y # CONFIG_CGROUP_PERF is not set # CONFIG_CGROUP_SCHED is not set # CONFIG_BLK_CGROUP is not set :-( > > The fact is, for desktop and server Linux, cgroups slowly becomes a > > mandatory thing. And the reason for this is that cgroups mechanism > > provides some very useful features (in an extensible way, like plugins), > > i.e. a way to manage and track processes and its resources -- which is the > > main purpose of cgroups. > > And for embedded and for real-time, some of us do not want cgroups to be > a mandatory thing. We want it to remain configurable. My personal > interest is in keeping the latency of certain critical paths (especially > in the scheduler) short and consistent. Much thanks for your input! That would be quite strong argument for going with /dev/mem_notify approach. Do you have any specific numbers how cgroups makes scheduler latencies worse? Thanks! -- Anton Vorontsov Email: cbouatmailru@xxxxxxxxx -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>