Hi.
On Fri, 24 Dec 2010 09:37:39 +0100
Johannes Weiner <hannes@xxxxxxxxxxx> wrote:
> 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/include/linux/memcontrol.h
> > +++ b/include/linux/memcontrol.h
> > @@ -146,6 +146,8 @@ unsigned long mem_cgroup_soft_limit_reclaim(struct zone *zone, int order,
> > gfp_t gfp_mask);
> > u64 mem_cgroup_get_limit(struct mem_cgroup *mem);
> >
> > +bool mem_cgroup_bad_page_check(struct page *page);
> > +void mem_cgroup_print_bad_page(struct page *page);
>
> Can you put those under CONFIG_DEBUG_VM and the dummies below under
> !CONFIG_CGROUP_MEM_RES_CTLR || !CONFIG_DEBUG_VM?
>
> The most likely configuration on distro kernels is memcg enabled and
> VM debugging disabled. It would be good to save the unneeded function
> calls in the allocator hotpath for the common case.
>
Will do.
> Also:
>
> > @@ -336,6 +338,16 @@ u64 mem_cgroup_get_limit(struct mem_cgroup *mem)
> > return 0;
> > }
> >
> > +static inline bool
> > +mem_cgroup_bad_page_check(struct page *page)
> > +{
> > + return false;
> > +}
> > +
> > +static void
>
> That needs an `inline' as well.
>
Will do.
> > --- 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;
> }
>
Nice idea.
> > +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.
Thank you for your reviews!
Daisuke Nishimura.
--
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 policy in Canada: sign http://dissolvethecrtc.ca/
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>