On Tue, 22 Feb 2011 18:12:54 +0100 Andrea Righi <arighi@xxxxxxxxxxx> wrote: > The page_cgroup infrastructure, currently available only for the memory > cgroup controller, can be used to store the owner of each page and > opportunely track the writeback IO. This information is encoded in > the upper 16-bits of the page_cgroup->flags. > > A owner can be identified using a generic ID number and the following > interfaces are provided to store a retrieve this information: > > unsigned long page_cgroup_get_owner(struct page *page); > int page_cgroup_set_owner(struct page *page, unsigned long id); > int page_cgroup_copy_owner(struct page *npage, struct page *opage); My immediate observation is that you're not really tracking the "owner" here - you're tracking an opaque 16-bit token known only to the block controller in a field which - if changed by anybody other than the block controller - will lead to mayhem in the block controller. I think it might be clearer - and safer - to say "blkcg" or some such instead of "owner" here. I'm tempted to say it might be better to just add a pointer to your throtl_grp structure into struct page_cgroup. Or maybe replace the mem_cgroup pointer with a single pointer to struct css_set. Both of those ideas, though, probably just add unwanted extra overhead now to gain generality which may or may not be wanted in the future. jon -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>