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Date: Tue, 14 Jun 2022 17:30:06 -0700
From: Wei Xu <weixugc@...gle.com>
To: Tim Chen <tim.c.chen@...ux.intel.com>
Cc: Linux MM <linux-mm@...ck.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Huang Ying <ying.huang@...el.com>,
Greg Thelen <gthelen@...gle.com>,
Yang Shi <shy828301@...il.com>,
Davidlohr Bueso <dave@...olabs.net>,
Brice Goglin <brice.goglin@...il.com>,
Michal Hocko <mhocko@...nel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Hesham Almatary <hesham.almatary@...wei.com>,
Dave Hansen <dave.hansen@...el.com>,
Jonathan Cameron <Jonathan.Cameron@...wei.com>,
Alistair Popple <apopple@...dia.com>,
Dan Williams <dan.j.williams@...el.com>,
Feng Tang <feng.tang@...el.com>,
Jagdish Gediya <jvgediya@...ux.ibm.com>,
Baolin Wang <baolin.wang@...ux.alibaba.com>,
David Rientjes <rientjes@...gle.com>,
"Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
Shakeel Butt <shakeelb@...gle.com>
Subject: Re: [RFC PATCH 2/3] mm/memory-tiers: Use page counter to track
toptier memory usage
(Resend in plain text. Sorry.)
On Tue, Jun 14, 2022 at 3:26 PM Tim Chen <tim.c.chen@...ux.intel.com> wrote:
>
> If we need to restrict toptier memory usage for a cgroup,
> we need to retrieve usage of toptier memory efficiently.
> Add a page counter to track toptier memory usage directly
> so its value can be returned right away.
> ---
> include/linux/memcontrol.h | 1 +
> mm/memcontrol.c | 50 ++++++++++++++++++++++++++++++++------
> 2 files changed, 43 insertions(+), 8 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 9ecead1042b9..b4f727cba1de 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -241,6 +241,7 @@ struct mem_cgroup {
>
> /* Accounted resources */
> struct page_counter memory; /* Both v1 & v2 */
> + struct page_counter toptier;
>
> union {
> struct page_counter swap; /* v2 only */
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 2f6e95e6d200..2f20ec2712b8 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -848,6 +848,23 @@ static void mem_cgroup_charge_statistics(struct mem_cgroup *memcg,
> __this_cpu_add(memcg->vmstats_percpu->nr_page_events, nr_pages);
> }
>
> +static inline void mem_cgroup_charge_toptier(struct mem_cgroup *memcg,
> + int nid,
> + int nr_pages)
> +{
> + if (!node_is_toptier(nid) || !memcg)
> + return;
> +
> + if (nr_pages >= 0) {
> + page_counter_charge(&memcg->toptier,
> + (unsigned long) nr_pages);
> + } else {
> + nr_pages = -nr_pages;
> + page_counter_uncharge(&memcg->toptier,
> + (unsigned long) nr_pages);
> + }
> +}
When we don't know which pages are being charged, we should still
charge the usage to toptier (assuming that toptier always include the
default tier), e.g. from try_charge_memcg().
The idea is that when lower tier memory is not used, memcg->toptier
and memcg->memory should have the same value. Otherwise, it can cause
confusions about where the pages of (memcg->memory - memcg->toptier)
go.
> static bool mem_cgroup_event_ratelimit(struct mem_cgroup *memcg,
> enum mem_cgroup_events_target target)
> {
> @@ -3027,6 +3044,8 @@ int __memcg_kmem_charge_page(struct page *page, gfp_t gfp, int order)
> if (!ret) {
> page->memcg_data = (unsigned long)objcg |
> MEMCG_DATA_KMEM;
> + mem_cgroup_charge_toptier(page_memcg(page),
> + page_to_nid(page), 1 << order);
> return 0;
> }
> obj_cgroup_put(objcg);
> @@ -3050,6 +3069,8 @@ void __memcg_kmem_uncharge_page(struct page *page, int order)
>
> objcg = __folio_objcg(folio);
> obj_cgroup_uncharge_pages(objcg, nr_pages);
> + mem_cgroup_charge_toptier(page_memcg(page),
> + page_to_nid(page), -nr_pages);
> folio->memcg_data = 0;
> obj_cgroup_put(objcg);
> }
> @@ -3947,13 +3968,10 @@ unsigned long mem_cgroup_memtier_usage(struct mem_cgroup *memcg,
>
> unsigned long mem_cgroup_toptier_usage(struct mem_cgroup *memcg)
> {
> - struct memory_tier *top_tier;
> -
> - top_tier = list_first_entry(&memory_tiers, struct memory_tier, list);
> - if (top_tier)
> - return mem_cgroup_memtier_usage(memcg, top_tier);
> - else
> + if (!memcg)
> return 0;
> +
> + return page_counter_read(&memcg->toptier);
> }
>
> #endif /* CONFIG_NUMA */
> @@ -5228,11 +5246,13 @@ mem_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
> memcg->oom_kill_disable = parent->oom_kill_disable;
>
> page_counter_init(&memcg->memory, &parent->memory);
> + page_counter_init(&memcg->toptier, &parent->toptier);
> page_counter_init(&memcg->swap, &parent->swap);
> page_counter_init(&memcg->kmem, &parent->kmem);
> page_counter_init(&memcg->tcpmem, &parent->tcpmem);
> } else {
> page_counter_init(&memcg->memory, NULL);
> + page_counter_init(&memcg->toptier, NULL);
> page_counter_init(&memcg->swap, NULL);
> page_counter_init(&memcg->kmem, NULL);
> page_counter_init(&memcg->tcpmem, NULL);
> @@ -5678,6 +5698,8 @@ static int mem_cgroup_move_account(struct page *page,
> memcg_check_events(to, nid);
> mem_cgroup_charge_statistics(from, -nr_pages);
> memcg_check_events(from, nid);
> + mem_cgroup_charge_toptier(to, nid, nr_pages);
> + mem_cgroup_charge_toptier(from, nid, -nr_pages);
> local_irq_enable();
> out_unlock:
> folio_unlock(folio);
> @@ -6761,6 +6783,7 @@ static int charge_memcg(struct folio *folio, struct mem_cgroup *memcg,
>
> local_irq_disable();
> mem_cgroup_charge_statistics(memcg, nr_pages);
> + mem_cgroup_charge_toptier(memcg, folio_nid(folio), nr_pages);
> memcg_check_events(memcg, folio_nid(folio));
> local_irq_enable();
> out:
> @@ -6853,6 +6876,7 @@ struct uncharge_gather {
> unsigned long nr_memory;
> unsigned long pgpgout;
> unsigned long nr_kmem;
> + unsigned long nr_toptier;
> int nid;
> };
>
> @@ -6867,6 +6891,7 @@ static void uncharge_batch(const struct uncharge_gather *ug)
>
> if (ug->nr_memory) {
> page_counter_uncharge(&ug->memcg->memory, ug->nr_memory);
> + page_counter_uncharge(&ug->memcg->toptier, ug->nr_toptier);
> if (do_memsw_account())
> page_counter_uncharge(&ug->memcg->memsw, ug->nr_memory);
> if (ug->nr_kmem)
> @@ -6929,12 +6954,18 @@ static void uncharge_folio(struct folio *folio, struct uncharge_gather *ug)
> ug->nr_memory += nr_pages;
> ug->nr_kmem += nr_pages;
>
> + if (node_is_toptier(folio_nid(folio)))
> + ug->nr_toptier += nr_pages;
> +
> folio->memcg_data = 0;
> obj_cgroup_put(objcg);
> } else {
> /* LRU pages aren't accounted at the root level */
> - if (!mem_cgroup_is_root(memcg))
> + if (!mem_cgroup_is_root(memcg)) {
> ug->nr_memory += nr_pages;
> + if (node_is_toptier(folio_nid(folio)))
> + ug->nr_toptier += nr_pages;
> + }
> ug->pgpgout++;
>
> folio->memcg_data = 0;
> @@ -7011,6 +7042,7 @@ void mem_cgroup_migrate(struct folio *old, struct folio *new)
> /* Force-charge the new page. The old one will be freed soon */
> if (!mem_cgroup_is_root(memcg)) {
> page_counter_charge(&memcg->memory, nr_pages);
> + mem_cgroup_charge_toptier(memcg, folio_nid(new), nr_pages);
> if (do_memsw_account())
> page_counter_charge(&memcg->memsw, nr_pages);
> }
> @@ -7231,8 +7263,10 @@ void mem_cgroup_swapout(struct folio *folio, swp_entry_t entry)
>
> folio->memcg_data = 0;
>
> - if (!mem_cgroup_is_root(memcg))
> + if (!mem_cgroup_is_root(memcg)) {
> page_counter_uncharge(&memcg->memory, nr_entries);
> + mem_cgroup_charge_toptier(memcg, folio_nid(folio), -nr_entries);
> + }
>
> if (!cgroup_memory_noswap && memcg != swap_memcg) {
> if (!mem_cgroup_is_root(swap_memcg))
> --
> 2.35.1
>
>
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