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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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