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Date: Thu, 23 Apr 2009 17:45:16 +0900
From: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"balbir@...ux.vnet.ibm.com" <balbir@...ux.vnet.ibm.com>,
"hugh@...itas.com" <hugh@...itas.com>
Subject: Re: [RFC][PATCH] fix swap entries is not reclaimed in proper way
for mem+swap controller
On Thu, 23 Apr 2009 13:14:37 +0900
Daisuke Nishimura <nishimura@....nes.nec.co.jp> wrote:
> > I'll dig and try more including another aproach..
> >
> How about this patch ?
>
> It seems to have been working fine for several hours.
> I should add more and more comments and clean it up, of course :)
> (I think it would be better to unify definitions of new functions to swapfile.c,
> and checking page_mapped() might be enough for mem_cgroup_free_unused_swapcache().)
>
> Signed-off-by: Daisuke Nishimura <nishimura@....nes.nec.co.jp>
Hmm, I still think this patch is overkill.
> ---
> include/linux/memcontrol.h | 5 +++
> include/linux/swap.h | 11 ++++++++
> mm/memcontrol.c | 62 ++++++++++++++++++++++++++++++++++++++++++++
> mm/swap_state.c | 8 +++++
> mm/swapfile.c | 32 ++++++++++++++++++++++-
> mm/vmscan.c | 8 +++++
> 6 files changed, 125 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 25b9ca9..8b674c2 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -101,6 +101,7 @@ struct zone_reclaim_stat *mem_cgroup_get_reclaim_stat(struct mem_cgroup *memcg,
> struct zone *zone);
> struct zone_reclaim_stat*
> mem_cgroup_get_reclaim_stat_from_page(struct page *page);
> +extern void mem_cgroup_free_unused_swapcache(struct page *page);
> extern void mem_cgroup_print_oom_info(struct mem_cgroup *memcg,
> struct task_struct *p);
>
> @@ -259,6 +260,10 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page)
> return NULL;
> }
>
> +static inline void mem_cgroup_free_unused_swapcache(struct page *page)
> +{
> +}
> +
> static inline void
> mem_cgroup_print_oom_info(struct mem_cgroup *memcg, struct task_struct *p)
> {
> diff --git a/include/linux/swap.h b/include/linux/swap.h
> index 62d8143..cdfa982 100644
> --- a/include/linux/swap.h
> +++ b/include/linux/swap.h
> @@ -336,11 +336,22 @@ static inline void disable_swap_token(void)
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR
> extern void mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent);
> +extern int mem_cgroup_fixup_swapin(struct page *page);
> +extern void mem_cgroup_fixup_swapfree(struct page *page);
> #else
> static inline void
> mem_cgroup_uncharge_swapcache(struct page *page, swp_entry_t ent)
> {
> }
> +static inline int
> +mem_cgroup_fixup_swapin(struct page *page)
> +{
> + return 0;
> +}
> +static inline void
> +mem_cgroup_fixup_swapfree(struct page *page)
> +{
> +}
> #endif
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> extern void mem_cgroup_uncharge_swap(swp_entry_t ent);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 79c32b8..f90967b 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -1536,6 +1536,68 @@ void mem_cgroup_uncharge_swap(swp_entry_t ent)
> }
> #endif
>
> +struct mem_cgroup_swap_fixup_work {
> + struct work_struct work;
> + struct page *page;
> +};
> +
> +static void mem_cgroup_fixup_swapfree_cb(struct work_struct *work)
> +{
> + struct mem_cgroup_swap_fixup_work *my_work;
> + struct page *page;
> +
> + my_work = container_of(work, struct mem_cgroup_swap_fixup_work, work);
> + page = my_work->page;
> +
> + lock_page(page);
> + if (PageSwapCache(page))
> + mem_cgroup_free_unused_swapcache(page);
> + unlock_page(page);
> +
> + kfree(my_work);
> + put_page(page);
> +}
> +
> +void mem_cgroup_fixup_swapfree(struct page *page)
> +{
> + struct mem_cgroup_swap_fixup_work *my_work;
> +
> + if (mem_cgroup_disabled())
> + return;
> +
> + if (!PageSwapCache(page) || page_mapped(page))
> + return;
> +
> + my_work = kmalloc(sizeof(*my_work), GFP_ATOMIC); /* cannot sleep */
> + if (my_work) {
> + get_page(page); /* put_page will be called in callback */
> + my_work->page = page;
> + INIT_WORK(&my_work->work, mem_cgroup_fixup_swapfree_cb);
> + schedule_work(&my_work->work);
> + }
> +
> + return;
> +}
> +
> +/*
> + * called from shrink_page_list() and mem_cgroup_fixup_swapfree_cb() to free
> + * !PageCgroupUsed SwapCache, because memcg cannot handle these SwapCache well.
> + */
> +void mem_cgroup_free_unused_swapcache(struct page *page)
> +{
> + struct page_cgroup *pc;
> +
> + VM_BUG_ON(!PageLocked(page));
> + VM_BUG_ON(!PageSwapCache(page));
> +
> + pc = lookup_page_cgroup(page);
> + /*
> + * Used bit of swapcache is solid under page lock.
> + */
> + if (!PageCgroupUsed(pc))
> + try_to_free_swap(page);
> +}
> +
> /*
> * Before starting migration, account PAGE_SIZE to mem_cgroup that the old
> * page belongs to.
> diff --git a/mm/swap_state.c b/mm/swap_state.c
> index 3ecea98..57d9678 100644
> --- a/mm/swap_state.c
> +++ b/mm/swap_state.c
> @@ -310,6 +310,14 @@ struct page *read_swap_cache_async(swp_entry_t entry, gfp_t gfp_mask,
> SetPageSwapBacked(new_page);
> err = add_to_swap_cache(new_page, entry, gfp_mask & GFP_KERNEL);
> if (likely(!err)) {
> + if (unlikely(mem_cgroup_fixup_swapin(new_page)))
> + /*
> + * new_page is not used by anyone.
> + * And it has been already removed from
> + * SwapCache and freed.
> + */
> + return NULL;
> +
Can't we check refcnt of swp_entry here, again ?
if (refcnt == 1), we can make this as STALE.
(and can free swap cache here)
Thanks,
-Kame
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