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Date: Thu, 15 Jun 2017 13:31:28 +1000
From: Balbir Singh <bsingharora@...il.com>
To: Jérôme Glisse <jglisse@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org,
John Hubbard <jhubbard@...dia.com>,
David Nellans <dnellans@...dia.com>,
Johannes Weiner <hannes@...xchg.org>,
Michal Hocko <mhocko@...nel.org>,
Vladimir Davydov <vdavydov.dev@...il.com>,
cgroups@...r.kernel.org
Subject: Re: [HMM-CDM 3/5] mm/memcontrol: allow to uncharge page without
using page->lru field
On Wed, 14 Jun 2017 16:11:42 -0400
Jérôme Glisse <jglisse@...hat.com> wrote:
> HMM pages (private or public device pages) are ZONE_DEVICE page and
> thus you can not use page->lru fields of those pages. This patch
> re-arrange the uncharge to allow single page to be uncharge without
> modifying the lru field of the struct page.
>
> There is no change to memcontrol logic, it is the same as it was
> before this patch.
>
> Signed-off-by: Jérôme Glisse <jglisse@...hat.com>
> Cc: Johannes Weiner <hannes@...xchg.org>
> Cc: Michal Hocko <mhocko@...nel.org>
> Cc: Vladimir Davydov <vdavydov.dev@...il.com>
> Cc: cgroups@...r.kernel.org
> ---
> mm/memcontrol.c | 168 +++++++++++++++++++++++++++++++-------------------------
> 1 file changed, 92 insertions(+), 76 deletions(-)
>
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e3fe4d0..b93f5fe 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5509,48 +5509,102 @@ void mem_cgroup_cancel_charge(struct page *page, struct mem_cgroup *memcg,
> cancel_charge(memcg, nr_pages);
> }
>
> -static void uncharge_batch(struct mem_cgroup *memcg, unsigned long pgpgout,
> - unsigned long nr_anon, unsigned long nr_file,
> - unsigned long nr_kmem, unsigned long nr_huge,
> - unsigned long nr_shmem, struct page *dummy_page)
> +struct uncharge_gather {
> + struct mem_cgroup *memcg;
> + unsigned long pgpgout;
> + unsigned long nr_anon;
> + unsigned long nr_file;
> + unsigned long nr_kmem;
> + unsigned long nr_huge;
> + unsigned long nr_shmem;
> + struct page *dummy_page;
> +};
> +
> +static inline void uncharge_gather_clear(struct uncharge_gather *ug)
> {
> - unsigned long nr_pages = nr_anon + nr_file + nr_kmem;
> + memset(ug, 0, sizeof(*ug));
> +}
> +
> +static void uncharge_batch(const struct uncharge_gather *ug)
> +{
Can we pass page as an argument so that we can do check events on the page?
> + unsigned long nr_pages = ug->nr_anon + ug->nr_file + ug->nr_kmem;
> unsigned long flags;
>
> - if (!mem_cgroup_is_root(memcg)) {
> - page_counter_uncharge(&memcg->memory, nr_pages);
> + if (!mem_cgroup_is_root(ug->memcg)) {
> + page_counter_uncharge(&ug->memcg->memory, nr_pages);
> if (do_memsw_account())
> - page_counter_uncharge(&memcg->memsw, nr_pages);
> - if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && nr_kmem)
> - page_counter_uncharge(&memcg->kmem, nr_kmem);
> - memcg_oom_recover(memcg);
> + page_counter_uncharge(&ug->memcg->memsw, nr_pages);
> + if (!cgroup_subsys_on_dfl(memory_cgrp_subsys) && ug->nr_kmem)
> + page_counter_uncharge(&ug->memcg->kmem, ug->nr_kmem);
> + memcg_oom_recover(ug->memcg);
> }
>
> local_irq_save(flags);
> - __this_cpu_sub(memcg->stat->count[MEMCG_RSS], nr_anon);
> - __this_cpu_sub(memcg->stat->count[MEMCG_CACHE], nr_file);
> - __this_cpu_sub(memcg->stat->count[MEMCG_RSS_HUGE], nr_huge);
> - __this_cpu_sub(memcg->stat->count[NR_SHMEM], nr_shmem);
> - __this_cpu_add(memcg->stat->events[PGPGOUT], pgpgout);
> - __this_cpu_add(memcg->stat->nr_page_events, nr_pages);
> - memcg_check_events(memcg, dummy_page);
> + __this_cpu_sub(ug->memcg->stat->count[MEMCG_RSS], ug->nr_anon);
> + __this_cpu_sub(ug->memcg->stat->count[MEMCG_CACHE], ug->nr_file);
> + __this_cpu_sub(ug->memcg->stat->count[MEMCG_RSS_HUGE], ug->nr_huge);
> + __this_cpu_sub(ug->memcg->stat->count[NR_SHMEM], ug->nr_shmem);
> + __this_cpu_add(ug->memcg->stat->events[PGPGOUT], ug->pgpgout);
> + __this_cpu_add(ug->memcg->stat->nr_page_events, nr_pages);
> + memcg_check_events(ug->memcg, ug->dummy_page);
> local_irq_restore(flags);
>
> - if (!mem_cgroup_is_root(memcg))
> - css_put_many(&memcg->css, nr_pages);
> + if (!mem_cgroup_is_root(ug->memcg))
> + css_put_many(&ug->memcg->css, nr_pages);
> +}
> +
> +static void uncharge_page(struct page *page, struct uncharge_gather *ug)
> +{
> + VM_BUG_ON_PAGE(PageLRU(page), page);
> + VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
> +
> + if (!page->mem_cgroup)
> + return;
> +
> + /*
> + * Nobody should be changing or seriously looking at
> + * page->mem_cgroup at this point, we have fully
> + * exclusive access to the page.
> + */
> +
> + if (ug->memcg != page->mem_cgroup) {
> + if (ug->memcg) {
> + uncharge_batch(ug);
What is ug->dummy_page set to at this point? ug->dummy_page is assigned below
> + uncharge_gather_clear(ug);
> + }
> + ug->memcg = page->mem_cgroup;
> + }
> +
> + if (!PageKmemcg(page)) {
> + unsigned int nr_pages = 1;
> +
> + if (PageTransHuge(page)) {
> + nr_pages <<= compound_order(page);
> + ug->nr_huge += nr_pages;
> + }
> + if (PageAnon(page))
> + ug->nr_anon += nr_pages;
> + else {
> + ug->nr_file += nr_pages;
> + if (PageSwapBacked(page))
> + ug->nr_shmem += nr_pages;
> + }
> + ug->pgpgout++;
> + } else {
> + ug->nr_kmem += 1 << compound_order(page);
> + __ClearPageKmemcg(page);
> + }
> +
> + ug->dummy_page = page;
> + page->mem_cgroup = NULL;
> }
>
> static void uncharge_list(struct list_head *page_list)
> {
> - struct mem_cgroup *memcg = NULL;
> - unsigned long nr_shmem = 0;
> - unsigned long nr_anon = 0;
> - unsigned long nr_file = 0;
> - unsigned long nr_huge = 0;
> - unsigned long nr_kmem = 0;
> - unsigned long pgpgout = 0;
> + struct uncharge_gather ug;
> struct list_head *next;
> - struct page *page;
> +
> + uncharge_gather_clear(&ug);
>
> /*
> * Note that the list can be a single page->lru; hence the
> @@ -5558,57 +5612,16 @@ static void uncharge_list(struct list_head *page_list)
> */
> next = page_list->next;
> do {
> + struct page *page;
> +
Nit pick
VM_WARN_ON(is_zone_device_page(page));
> page = list_entry(next, struct page, lru);
> next = page->lru.next;
>
> - VM_BUG_ON_PAGE(PageLRU(page), page);
> - VM_BUG_ON_PAGE(!PageHWPoison(page) && page_count(page), page);
> -
> - if (!page->mem_cgroup)
> - continue;
> -
> - /*
> - * Nobody should be changing or seriously looking at
> - * page->mem_cgroup at this point, we have fully
> - * exclusive access to the page.
> - */
> -
> - if (memcg != page->mem_cgroup) {
> - if (memcg) {
> - uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
> - nr_kmem, nr_huge, nr_shmem, page);
> - pgpgout = nr_anon = nr_file = nr_kmem = 0;
> - nr_huge = nr_shmem = 0;
> - }
> - memcg = page->mem_cgroup;
> - }
> -
> - if (!PageKmemcg(page)) {
> - unsigned int nr_pages = 1;
> -
> - if (PageTransHuge(page)) {
> - nr_pages <<= compound_order(page);
> - nr_huge += nr_pages;
> - }
> - if (PageAnon(page))
> - nr_anon += nr_pages;
> - else {
> - nr_file += nr_pages;
> - if (PageSwapBacked(page))
> - nr_shmem += nr_pages;
> - }
> - pgpgout++;
> - } else {
> - nr_kmem += 1 << compound_order(page);
> - __ClearPageKmemcg(page);
> - }
> -
> - page->mem_cgroup = NULL;
> + uncharge_page(page, &ug);
> } while (next != page_list);
>
> - if (memcg)
> - uncharge_batch(memcg, pgpgout, nr_anon, nr_file,
> - nr_kmem, nr_huge, nr_shmem, page);
> + if (ug.memcg)
> + uncharge_batch(&ug);
> }
>
> /**
> @@ -5620,6 +5633,8 @@ static void uncharge_list(struct list_head *page_list)
> */
> void mem_cgroup_uncharge(struct page *page)
> {
> + struct uncharge_gather ug;
> +
> if (mem_cgroup_disabled())
> return;
>
> @@ -5627,8 +5642,9 @@ void mem_cgroup_uncharge(struct page *page)
> if (!page->mem_cgroup)
> return;
>
> - INIT_LIST_HEAD(&page->lru);
> - uncharge_list(&page->lru);
> + uncharge_gather_clear(&ug);
> + uncharge_page(page, &ug);
> + uncharge_batch(&ug);
> }
Balbir Singh.
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