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SubjectRe: [BUGFIX][PATCH 1/4] memcg: fix limit estimation at reclaim for hugepage
On Fri, 28 Jan 2011 13:40:19 +0900
Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:

> On Fri, 28 Jan 2011 12:24:49 +0900
> KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote:
>
> > From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> >
> > Current memory cgroup's code tends to assume page_size == PAGE_SIZE
> > and arrangement for THP is not enough yet.
> >
> > This is one of fixes for supporing THP. This adds
> > mem_cgroup_check_margin() and checks whether there are required amount of
> > free resource after memory reclaim. By this, THP page allocation
> > can know whether it really succeeded or not and avoid infinite-loop
> > and hangup.
> >
> > Total fixes for do_charge()/reclaim memory will follow this patch.
> >
> > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
>
> This patch looks good to me, but some nitpicks.
>
> > ---
> > include/linux/res_counter.h | 11 +++++++++++
> > mm/memcontrol.c | 25 ++++++++++++++++++++++++-
> > 2 files changed, 35 insertions(+), 1 deletion(-)
> >
> > Index: mmotm-0125/include/linux/res_counter.h
> > ===================================================================
> > --- mmotm-0125.orig/include/linux/res_counter.h
> > +++ mmotm-0125/include/linux/res_counter.h
> > @@ -182,6 +182,17 @@ static inline bool res_counter_check_und
> > return ret;
> > }
> >
> > +static inline s64 res_counter_check_margin(struct res_counter *cnt)
> > +{
> > + s64 ret;
> > + unsigned long flags;
> > +
> > + spin_lock_irqsave(&cnt->lock, flags);
> > + ret = cnt->limit - cnt->usage;
> > + spin_unlock_irqrestore(&cnt->lock, flags);
> > + return ret;
> > +}
> > +
> > static inline bool res_counter_check_under_soft_limit(struct res_counter *cnt)
> > {
> > bool ret;
> > Index: mmotm-0125/mm/memcontrol.c
> > ===================================================================
> > --- mmotm-0125.orig/mm/memcontrol.c
> > +++ mmotm-0125/mm/memcontrol.c
> > @@ -1111,6 +1111,22 @@ static bool mem_cgroup_check_under_limit
> > return false;
> > }
> >
> > +static s64 mem_cgroup_check_margin(struct mem_cgroup *mem)
> > +{
> > + s64 mem_margin;
> > +
> > + if (do_swap_account) {
> > + s64 memsw_margin;
> > +
> > + mem_margin = res_counter_check_margin(&mem->res);
> > + memsw_margin = res_counter_check_margin(&mem->memsw);
> > + if (mem_margin > memsw_margin)
> > + mem_margin = memsw_margin;
> > + } else
> > + mem_margin = res_counter_check_margin(&mem->res);
> > + return mem_margin;
> > +}
> > +
> How about
>
> mem_margin = res_counter_check_margin(&mem->res);
> if (do_swap_account)
> memsw_margin = res_counter_check_margin(&mem->memsw);
> else
> memsw_margin = RESOURCE_MAX;
>
> return min(mem_margin, memsw_margin);
>
> ?
> I think using min() makes it more clear what this function does.
>

Ok.

> > static unsigned int get_swappiness(struct mem_cgroup *memcg)
> > {
> > struct cgroup *cgrp = memcg->css.cgroup;
> > @@ -1853,7 +1869,14 @@ static int __mem_cgroup_do_charge(struct
> > * Check the limit again to see if the reclaim reduced the
> > * current usage of the cgroup before giving up
> > */
> > - if (ret || mem_cgroup_check_under_limit(mem_over_limit))
> > + if (mem_cgroup_check_margin(mem_over_limit) >= csize)
> > + return CHARGE_RETRY;
> > +
> > + /*
> > + * If the charge size is a PAGE_SIZE, it's not hopeless while
> > + * we can reclaim a page.
> > + */
> > + if (csize == PAGE_SIZE && ret)
> > return CHARGE_RETRY;
> >
> > /*
> >
> checkpatch complains some whitespace warnings.
>
will fix soon.

-Kame



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