On Fri, Dec 24, 2010 at 09:31:31AM +0900, Daisuke Nishimura wrote:
> From: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
>
> This patch add checks at allocating or freeing a page whether the page is used
> (iow, charged) from the view point of memcg.
> This check may be usefull in debugging a problem and we did a similar checks
> before the commit 52d4b9ac(memcg: allocate all page_cgroup at boot).
>
> This patch adds some overheads at allocating or freeing memory, so it's enabled
> only when CONFIG_DEBUG_VM is enabled.
>
> Signed-off-by: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -2971,6 +2971,53 @@ int mem_cgroup_shmem_charge_fallback(struct page *page,
> return ret;
> }
>
> +#ifdef CONFIG_DEBUG_VM
> +static bool
> +__mem_cgroup_bad_page_check(struct page *page, struct page_cgroup **pcp)
> +{
> + struct page_cgroup *pc;
> + bool ret = false;
> +
> + pc = lookup_page_cgroup(page);
> + if (unlikely(!pc))
> + goto out;
> +
> + if (PageCgroupUsed(pc)) {
> + ret = true;
> + if (pcp)
> + *pcp = pc;
> + }
> +out:
> + return ret;
I think it is not necessary to have two return values. Just return
the pc if it's in use:
static struct page_cgroup *lookup_page_cgroup_used(struct page)
{
struct page_cgroup *pc;
pc = lookup_page_cgroup(page);
if (likely(pc) && PageCgroupUsed(pc))
return pc;
return NULL;
}
> +bool mem_cgroup_bad_page_check(struct page *page)
> +{
> + if (mem_cgroup_disabled())
> + return false;
> +
> + return __mem_cgroup_bad_page_check(page, NULL);
return !!lookup_page_cgroup_used(page);
> +void mem_cgroup_print_bad_page(struct page *page)
> +{
> + struct page_cgroup *pc;
> +
> + if (__mem_cgroup_bad_page_check(page, &pc))
> + printk(KERN_ALERT "pc:%p pc->flags:%ld pc->mem_cgroup:%p\n",
> + pc, pc->flags, pc->mem_cgroup);
pc = lookup_page_cgroup_used(page);
if (pc)
printk()
Other than that, I agree with the patch.
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