On Wed, 23 Feb 2011 09:59:11 +0100
Andrea Righi [off-list ref] wrote:

quoted

I wonder I can make pc->mem_cgroup to be pc->memid(16bit), then, 
==
static inline struct mem_cgroup *get_memcg_from_pc(struct page_cgroup *pc)
{
    struct cgroup_subsys_state *css = css_lookup(&mem_cgroup_subsys, pc->memid);
    return container_of(css, struct mem_cgroup, css);
}
==
Overhead will be seen at updating file statistics and LRU management.

But, hmm, can't you do that tracking without page_cgroup ?
Because the number of dirty/writeback pages are far smaller than total pages,
chasing I/O with dynamic structure is not very bad..

prepareing [pfn -> blkio] record table and move that information to struct bio
in dynamic way is very difficult ?

This would be ok for dirty pages, but consider that we're also tracking
anonymous pages. So, if we want to control the swap IO we actually need
to save this information for a lot of pages and at the end I think we'll
basically duplicate the page_cgroup code.

swap io is always started with bio and the task/mm_struct.
So, if we can record information in bio, no page tracking is required.
You can record information to bio just by reading mm->owner.

Thanks,
-Kame

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