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SubjectRe: [PATCH v9 2/8] hugetlb_cgroup: add interface for charge/uncharge hugetlb reservations
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On 12/17/19 3:16 PM, Mina Almasry wrote:
> Augments hugetlb_cgroup_charge_cgroup to be able to charge hugetlb
> usage or hugetlb reservation counter.
>
> Adds a new interface to uncharge a hugetlb_cgroup counter via
> hugetlb_cgroup_uncharge_counter.
>
> Integrates the counter with hugetlb_cgroup, via hugetlb_cgroup_init,
> hugetlb_cgroup_have_usage, and hugetlb_cgroup_css_offline.
>
> Signed-off-by: Mina Almasry <almasrymina@google.com>
>
> ---
>
> Changes in V9:
> - Fixed HUGETLB_CGROUP_MIN_ORDER.
> - Minor variable name update.
> - Moved some init/cleanup code from later patches in the series to this patch.
> - Updated reparenting of reservation accounting.
>
> ---
> include/linux/hugetlb_cgroup.h | 68 ++++++++++++++---------
> mm/hugetlb.c | 19 ++++---
> mm/hugetlb_cgroup.c | 98 +++++++++++++++++++++++++---------
> 3 files changed, 127 insertions(+), 58 deletions(-)
>
> diff --git a/include/linux/hugetlb_cgroup.h b/include/linux/hugetlb_cgroup.h
> index 063962f6dfc6a..eab8a70d5bcb5 100644
> --- a/include/linux/hugetlb_cgroup.h
> +++ b/include/linux/hugetlb_cgroup.h
> @@ -20,29 +20,37 @@
> struct hugetlb_cgroup;
> /*
> * Minimum page order trackable by hugetlb cgroup.
> - * At least 3 pages are necessary for all the tracking information.
> + * At least 4 pages are necessary for all the tracking information.
> */
> #define HUGETLB_CGROUP_MIN_ORDER 2
>
> #ifdef CONFIG_CGROUP_HUGETLB
>
> -static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
> +static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page,
> + bool reserved)
> {
> VM_BUG_ON_PAGE(!PageHuge(page), page);
>
> if (compound_order(page) < HUGETLB_CGROUP_MIN_ORDER)
> return NULL;
> - return (struct hugetlb_cgroup *)page[2].private;
> + if (reserved)
> + return (struct hugetlb_cgroup *)page[3].private;
> + else
> + return (struct hugetlb_cgroup *)page[2].private;
> }
>
> -static inline
> -int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
> +static inline int set_hugetlb_cgroup(struct page *page,
> + struct hugetlb_cgroup *h_cg,
> + bool reservation)
> {
> VM_BUG_ON_PAGE(!PageHuge(page), page);
>
> if (compound_order(page) < HUGETLB_CGROUP_MIN_ORDER)
> return -1;
> - page[2].private = (unsigned long)h_cg;
> + if (reservation)
> + page[3].private = (unsigned long)h_cg;
> + else
> + page[2].private = (unsigned long)h_cg;
> return 0;
> }
>
> @@ -52,26 +60,34 @@ static inline bool hugetlb_cgroup_disabled(void)
> }
>
> extern int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup **ptr);
> + struct hugetlb_cgroup **ptr,
> + bool reserved);
> extern void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> struct hugetlb_cgroup *h_cg,
> - struct page *page);
> + struct page *page, bool reserved);
> extern void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
> - struct page *page);
> + struct page *page, bool reserved);
> +
> extern void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup *h_cg);
> + struct hugetlb_cgroup *h_cg,
> + bool reserved);
> +extern void hugetlb_cgroup_uncharge_counter(struct page_counter *p,
> + unsigned long nr_pages,
> + struct cgroup_subsys_state *css);
> +

Do we need a corresponding stub for the !CONFIG_CGROUP_HUGETLB case?

> extern void hugetlb_cgroup_file_init(void) __init;
> extern void hugetlb_cgroup_migrate(struct page *oldhpage,
> struct page *newhpage);
>
> #else
> -static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page)
> +static inline struct hugetlb_cgroup *hugetlb_cgroup_from_page(struct page *page,
> + bool reserved)
> {
> return NULL;
> }
>
> -static inline
> -int set_hugetlb_cgroup(struct page *page, struct hugetlb_cgroup *h_cg)
> +static inline int set_hugetlb_cgroup(struct page *page,
> + struct hugetlb_cgroup *h_cg, bool reserved)
> {
> return 0;
> }
> @@ -81,28 +97,30 @@ static inline bool hugetlb_cgroup_disabled(void)
> return true;
> }
>
> -static inline int
> -hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup **ptr)
> +static inline int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> + struct hugetlb_cgroup **ptr,
> + bool reserved)
> {
> return 0;
> }
>
> -static inline void
> -hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup *h_cg,
> - struct page *page)
> +static inline void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> + struct hugetlb_cgroup *h_cg,
> + struct page *page,
> + bool reserved)
> {
> }
>
> -static inline void
> -hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages, struct page *page)
> +static inline void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
> + struct page *page,
> + bool reserved)
> {
> }
>
> -static inline void
> -hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup *h_cg)
> +static inline void hugetlb_cgroup_uncharge_cgroup(int idx,
> + unsigned long nr_pages,
> + struct hugetlb_cgroup *h_cg,
> + bool reserved)
> {
> }
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index ac65bb5e38ac2..e6e8240f1718c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -1067,7 +1067,8 @@ static void update_and_free_page(struct hstate *h, struct page *page)
> 1 << PG_active | 1 << PG_private |
> 1 << PG_writeback);
> }
> - VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page), page);
> + VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page, false), page);
> + VM_BUG_ON_PAGE(hugetlb_cgroup_from_page(page, true), page);
> set_compound_page_dtor(page, NULL_COMPOUND_DTOR);
> set_page_refcounted(page);
> if (hstate_is_gigantic(h)) {
> @@ -1177,8 +1178,8 @@ void free_huge_page(struct page *page)
>
> spin_lock(&hugetlb_lock);
> clear_page_huge_active(page);
> - hugetlb_cgroup_uncharge_page(hstate_index(h),
> - pages_per_huge_page(h), page);
> + hugetlb_cgroup_uncharge_page(hstate_index(h), pages_per_huge_page(h),
> + page, false);

hugetlb code has been restructured a bit and this now resides in the
function __free_huge_page().

> if (restore_reserve)
> h->resv_huge_pages++;
>
> @@ -1204,7 +1205,8 @@ static void prep_new_huge_page(struct hstate *h, struct page *page, int nid)
> INIT_LIST_HEAD(&page->lru);
> set_compound_page_dtor(page, HUGETLB_PAGE_DTOR);
> spin_lock(&hugetlb_lock);
> - set_hugetlb_cgroup(page, NULL);
> + set_hugetlb_cgroup(page, NULL, false);
> + set_hugetlb_cgroup(page, NULL, true);
> h->nr_huge_pages++;
> h->nr_huge_pages_node[nid]++;
> spin_unlock(&hugetlb_lock);
> @@ -1990,7 +1992,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> gbl_chg = 1;
> }
>
> - ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg);
> + ret = hugetlb_cgroup_charge_cgroup(idx, pages_per_huge_page(h), &h_cg,
> + false);
> if (ret)
> goto out_subpool_put;
>
> @@ -2014,7 +2017,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> list_move(&page->lru, &h->hugepage_activelist);
> /* Fall through */
> }
> - hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page);
> + hugetlb_cgroup_commit_charge(idx, pages_per_huge_page(h), h_cg, page,
> + false);
> spin_unlock(&hugetlb_lock);
>
> set_page_private(page, (unsigned long)spool);
> @@ -2038,7 +2042,8 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> return page;
>
> out_uncharge_cgroup:
> - hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg);
> + hugetlb_cgroup_uncharge_cgroup(idx, pages_per_huge_page(h), h_cg,
> + false);
> out_subpool_put:
> if (map_chg || avoid_reserve)
> hugepage_subpool_put_pages(spool, 1);
> diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c
> index 35415af9ed26f..b03270b0d5833 100644
> --- a/mm/hugetlb_cgroup.c
> +++ b/mm/hugetlb_cgroup.c
> @@ -96,8 +96,12 @@ static inline bool hugetlb_cgroup_have_usage(struct hugetlb_cgroup *h_cg)
> int idx;
>
> for (idx = 0; idx < hugetlb_max_hstate; idx++) {
> - if (page_counter_read(&h_cg->hugepage[idx]))
> + if (page_counter_read(
> + hugetlb_cgroup_get_counter(h_cg, idx, true)) ||
> + page_counter_read(
> + hugetlb_cgroup_get_counter(h_cg, idx, false))) {
> return true;
> + }
> }
> return false;
> }
> @@ -108,18 +112,32 @@ static void hugetlb_cgroup_init(struct hugetlb_cgroup *h_cgroup,
> int idx;
>
> for (idx = 0; idx < HUGE_MAX_HSTATE; idx++) {
> - struct page_counter *counter = &h_cgroup->hugepage[idx];
> - struct page_counter *parent = NULL;
> + struct page_counter *fault_parent = NULL;
> + struct page_counter *reserved_parent = NULL;
> unsigned long limit;
> int ret;
>
> - if (parent_h_cgroup)
> - parent = &parent_h_cgroup->hugepage[idx];
> - page_counter_init(counter, parent);
> + if (parent_h_cgroup) {
> + fault_parent = hugetlb_cgroup_get_counter(
> + parent_h_cgroup, idx, false);
> + reserved_parent = hugetlb_cgroup_get_counter(
> + parent_h_cgroup, idx, true);
> + }
> + page_counter_init(hugetlb_cgroup_get_counter(h_cgroup, idx,
> + false),
> + fault_parent);
> + page_counter_init(hugetlb_cgroup_get_counter(h_cgroup, idx,
> + true),
> + reserved_parent);
>
> limit = round_down(PAGE_COUNTER_MAX,
> 1 << huge_page_order(&hstates[idx]));
> - ret = page_counter_set_max(counter, limit);
> +
> + ret = page_counter_set_max(
> + hugetlb_cgroup_get_counter(h_cgroup, idx, false),
> + limit);
> + ret = page_counter_set_max(
> + hugetlb_cgroup_get_counter(h_cgroup, idx, true), limit);
> VM_BUG_ON(ret);

The second page_counter_set_max() call overwrites ret before the check in
VM_BUG_ON().

> }
> }
> @@ -149,7 +167,6 @@ static void hugetlb_cgroup_css_free(struct cgroup_subsys_state *css)
> kfree(h_cgroup);
> }
>
> -
> /*
> * Should be called with hugetlb_lock held.
> * Since we are holding hugetlb_lock, pages cannot get moved from
> @@ -165,7 +182,7 @@ static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup *h_cg,
> struct hugetlb_cgroup *page_hcg;
> struct hugetlb_cgroup *parent = parent_hugetlb_cgroup(h_cg);
>
> - page_hcg = hugetlb_cgroup_from_page(page);
> + page_hcg = hugetlb_cgroup_from_page(page, false);
> /*
> * We can have pages in active list without any cgroup
> * ie, hugepage with less than 3 pages. We can safely
> @@ -184,7 +201,7 @@ static void hugetlb_cgroup_move_parent(int idx, struct hugetlb_cgroup *h_cg,
> /* Take the pages off the local counter */
> page_counter_cancel(counter, nr_pages);
>
> - set_hugetlb_cgroup(page, parent);
> + set_hugetlb_cgroup(page, parent, false);
> out:
> return;
> }
> @@ -227,7 +244,7 @@ static inline void hugetlb_event(struct hugetlb_cgroup *hugetlb, int idx,
> }
>
> int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup **ptr)
> + struct hugetlb_cgroup **ptr, bool reserved)
> {
> int ret = 0;
> struct page_counter *counter;
> @@ -250,13 +267,20 @@ int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> }
> rcu_read_unlock();
>
> - if (!page_counter_try_charge(&h_cg->hugepage[idx], nr_pages,
> - &counter)) {
> + if (!page_counter_try_charge(hugetlb_cgroup_get_counter(h_cg, idx,
> + reserved),
> + nr_pages, &counter)) {
> ret = -ENOMEM;
> hugetlb_event(hugetlb_cgroup_from_counter(counter, idx), idx,
> HUGETLB_MAX);
> + css_put(&h_cg->css);
> + goto done;
> }
> - css_put(&h_cg->css);
> + /* Reservations take a reference to the css because they do not get
> + * reparented.

I'm hoping someone with more cgroup knowledge can comment on this and any
consequences of not reparenting reservations. We previously talked about
why reparenting would be very difficult/expensive. I understand why you are
nopt doing it. Just do not fully understand what needs to be done from the
cgroup side.

Several of the following modifications deal with this.
--
Mike kravetz

> + */
> + if (!reserved)
> + css_put(&h_cg->css);
> done:
> *ptr = h_cg;
> return ret;
> @@ -265,12 +289,12 @@ int hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages,
> /* Should be called with hugetlb_lock held */
> void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> struct hugetlb_cgroup *h_cg,
> - struct page *page)
> + struct page *page, bool reserved)
> {
> if (hugetlb_cgroup_disabled() || !h_cg)
> return;
>
> - set_hugetlb_cgroup(page, h_cg);
> + set_hugetlb_cgroup(page, h_cg, reserved);
> return;
> }
>
> @@ -278,23 +302,29 @@ void hugetlb_cgroup_commit_charge(int idx, unsigned long nr_pages,
> * Should be called with hugetlb_lock held
> */
> void hugetlb_cgroup_uncharge_page(int idx, unsigned long nr_pages,
> - struct page *page)
> + struct page *page, bool reserved)
> {
> struct hugetlb_cgroup *h_cg;
>
> if (hugetlb_cgroup_disabled())
> return;
> lockdep_assert_held(&hugetlb_lock);
> - h_cg = hugetlb_cgroup_from_page(page);
> + h_cg = hugetlb_cgroup_from_page(page, reserved);
> if (unlikely(!h_cg))
> return;
> - set_hugetlb_cgroup(page, NULL);
> - page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
> + set_hugetlb_cgroup(page, NULL, reserved);
> +
> + page_counter_uncharge(hugetlb_cgroup_get_counter(h_cg, idx, reserved),
> + nr_pages);
> +
> + if (reserved)
> + css_put(&h_cg->css);
> +
> return;
> }
>
> void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
> - struct hugetlb_cgroup *h_cg)
> + struct hugetlb_cgroup *h_cg, bool reserved)
> {
> if (hugetlb_cgroup_disabled() || !h_cg)
> return;
> @@ -302,8 +332,22 @@ void hugetlb_cgroup_uncharge_cgroup(int idx, unsigned long nr_pages,
> if (huge_page_order(&hstates[idx]) < HUGETLB_CGROUP_MIN_ORDER)
> return;
>
> - page_counter_uncharge(&h_cg->hugepage[idx], nr_pages);
> - return;
> + page_counter_uncharge(hugetlb_cgroup_get_counter(h_cg, idx, reserved),
> + nr_pages);
> +
> + if (reserved)
> + css_put(&h_cg->css);
> +}
> +
> +void hugetlb_cgroup_uncharge_counter(struct page_counter *p,
> + unsigned long nr_pages,
> + struct cgroup_subsys_state *css)
> +{
> + if (hugetlb_cgroup_disabled() || !p || !css)
> + return;
> +
> + page_counter_uncharge(p, nr_pages);
> + css_put(css);
> }
>
> enum {
> @@ -678,6 +722,7 @@ void __init hugetlb_cgroup_file_init(void)
> void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
> {
> struct hugetlb_cgroup *h_cg;
> + struct hugetlb_cgroup *h_cg_reservation;
> struct hstate *h = page_hstate(oldhpage);
>
> if (hugetlb_cgroup_disabled())
> @@ -685,11 +730,12 @@ void hugetlb_cgroup_migrate(struct page *oldhpage, struct page *newhpage)
>
> VM_BUG_ON_PAGE(!PageHuge(oldhpage), oldhpage);
> spin_lock(&hugetlb_lock);
> - h_cg = hugetlb_cgroup_from_page(oldhpage);
> - set_hugetlb_cgroup(oldhpage, NULL);
> + h_cg = hugetlb_cgroup_from_page(oldhpage, false);
> + h_cg_reservation = hugetlb_cgroup_from_page(oldhpage, true);
> + set_hugetlb_cgroup(oldhpage, NULL, false);
>
> /* move the h_cg details to new cgroup */
> - set_hugetlb_cgroup(newhpage, h_cg);
> + set_hugetlb_cgroup(newhpage, h_cg_reservation, true);
> list_move(&newhpage->lru, &h->hugepage_activelist);
> spin_unlock(&hugetlb_lock);
> return;
> --
> 2.24.1.735.g03f4e72817-goog
>

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