Messages in this thread | | | Date | Fri, 16 Jan 2009 15:35:41 +0800 | From | Li Zefan <> | Subject | Re: [PATCH 3/4] memcg: hierarchical reclaim by CSS ID |
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>>>>> + while (!ret) { >>>>> + rcu_read_lock(); >>>>> + nextid = root_mem->last_scanned_child + 1; >>>>> + css = css_get_next(&mem_cgroup_subsys, nextid, &root_mem->css, >>>>> + &found); >>>>> + if (css && css_is_populated(css) && css_tryget(css)) >>>> I don't see why you need to check css_is_populated(css) ? >>>> >>> Main reason is for sanity. I don't like to hold css->refcnt of not populated css. >> I think this is a rare case. It's just a very short period when a cgroup is >> being created but not yet fully created. >> >>> Second reason is for avoinding unnecessary calls to try_to_free_pages(), >>> it's heavy. I should also add mem->res.usage == 0 case for skipping but not yet. >>> >> And if mem->res.usage == 0 is checked, css_is_popuated() is just redundant. >> > Hmm ? Can I check mem->res.usage before css_tryget() ? >
I think you can. If css != NULL, css is valid (otherwise how can we access css->flags in css_tryget), so mem is valid. Correct me if I'm wrong. :)
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