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Mon, 28 Sep 2026 12:23:53 -0700 (PDT) From: Joshua Hahn To: Johannes Weiner , Michal Hocko , Shakeel Butt Cc: Roman Gushchin , Muchun Song , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Maarten Lankhorst , Maxime Ripard , Natalie Vock , Tejun Heo , =?UTF-8?q?Michal=20Koutn=C3=BD?= , Oscar Salvador , cgroups@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com Subject: [PATCH v6 RESEND 3/5] mm/page_counter: make page_counter_try_charge() stock-aware Date: Mon, 28 Sep 2026 12:23:46 -0700 Message-ID: <20260928192349.3432886-4-joshua.hahnjy@gmail.com> X-Mailer: git-send-email 2.53.0 In-Reply-To: <20260928192349.3432886-1-joshua.hahnjy@gmail.com> References: <20260928192349.3432886-1-joshua.hahnjy@gmail.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Stat-Signature: 6hk8aip1tzwookuphmukxff67o9s5ewb X-Rspamd-Queue-Id: EEEAC40007 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1790623434-129477 X-HE-Meta: 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 zpkgRYqf 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Make page_counter_try_charge() consume stock transparently to callers while preserving the same semantics as try_charge_memcg's greedy charge attempt, refill, and !allow_spinning special case. page_counter_try_charge gets two new parameters, may_batch and nr_charged. may_batch is intended to preserve the behavior of !allow_spinning scenarios in try_charge_memcg, where the goal is to charge as quickly as possible, without evicting other stock slots or making a greedy charge to refill the stock. nr_charged is used to reflect the size of the successful hierarchy charge, preserving the existing batch-based memory.high accounting for current->memcg_nr_pages_over_high. As with refill_stock() today, the full charge is reported even if the excess is later uncharged because the stock could not accept it. This only affects memory.high throttling heuristics and never fails a charge. This behavior may be fixed to properly account the net charge in a future follow-up. As of this patch, no page_counter has stock yet, so there are no functional changes intended. Signed-off-by: Joshua Hahn --- include/linux/page_counter.h | 4 +- kernel/cgroup/dmem.c | 2 +- mm/hugetlb_cgroup.c | 2 +- mm/memcontrol-v1.c | 3 +- mm/memcontrol.c | 8 ++-- mm/page_counter.c | 82 +++++++++++++++++++++++++++++++----- 6 files changed, 83 insertions(+), 18 deletions(-) diff --git a/include/linux/page_counter.h b/include/linux/page_counter.h index cf627c5090093..58532259e7f59 100644 --- a/include/linux/page_counter.h +++ b/include/linux/page_counter.h @@ -98,8 +98,8 @@ long page_counter_margin(const struct page_counter *counter); void page_counter_cancel(struct page_counter *counter, unsigned long nr_pages); void page_counter_charge(struct page_counter *counter, unsigned long nr_pages); bool page_counter_try_charge(struct page_counter *counter, - unsigned long nr_pages, - struct page_counter **fail); + unsigned long nr_pages, struct page_counter **fail, + bool may_batch, unsigned long *nr_charged); void page_counter_refill_stock(struct page_counter *counter, unsigned long nr_pages); void page_counter_drain_stock_fully(struct page_counter_stock_pcp *stock); diff --git a/kernel/cgroup/dmem.c b/kernel/cgroup/dmem.c index 4683f3d680226..569307aa4bd62 100644 --- a/kernel/cgroup/dmem.c +++ b/kernel/cgroup/dmem.c @@ -736,7 +736,7 @@ int dmem_cgroup_try_charge(struct dmem_cgroup_region *region, u64 size, goto err; } - if (!page_counter_try_charge(&pool->cnt, size, &fail)) { + if (!page_counter_try_charge(&pool->cnt, size, &fail, false, NULL)) { if (ret_limit_pool) { *ret_limit_pool = container_of(fail, struct dmem_cgroup_pool_state, cnt); css_get(&(*ret_limit_pool)->cs->css); diff --git a/mm/hugetlb_cgroup.c b/mm/hugetlb_cgroup.c index 3fb41311e4c7d..bbc2dd3fa3c97 100644 --- a/mm/hugetlb_cgroup.c +++ b/mm/hugetlb_cgroup.c @@ -304,7 +304,7 @@ static int __hugetlb_cgroup_charge_cgroup(int idx, unsigned long nr_pages, if (!page_counter_try_charge( __hugetlb_cgroup_counter_from_cgroup(h_cg, idx, rsvd), - nr_pages, &counter)) { + nr_pages, &counter, false, NULL)) { ret = -ENOMEM; hugetlb_event(h_cg, idx, HUGETLB_MAX); css_put(&h_cg->css); diff --git a/mm/memcontrol-v1.c b/mm/memcontrol-v1.c index b7f2868885071..a146e54c6f9f7 100644 --- a/mm/memcontrol-v1.c +++ b/mm/memcontrol-v1.c @@ -2193,7 +2193,8 @@ bool memcg1_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages, { struct page_counter *fail; - if (page_counter_try_charge(&memcg->tcpmem, nr_pages, &fail)) { + if (page_counter_try_charge(&memcg->tcpmem, nr_pages, &fail, + false, NULL)) { memcg->tcpmem_pressure = 0; return true; } diff --git a/mm/memcontrol.c b/mm/memcontrol.c index edb2da5a326c5..53be4365e2c9e 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2722,13 +2722,14 @@ static int try_charge_memcg(struct mem_cgroup *memcg, gfp_t gfp_mask, reclaim_options = MEMCG_RECLAIM_MAY_SWAP; if (do_memsw_account() && - !page_counter_try_charge(&memcg->memsw, batch, &counter)) { + !page_counter_try_charge(&memcg->memsw, batch, &counter, false, + NULL)) { mem_over_limit = mem_cgroup_from_counter(counter, memsw); reclaim_options &= ~MEMCG_RECLAIM_MAY_SWAP; goto reclaim; } - if (page_counter_try_charge(&memcg->memory, batch, &counter)) + if (page_counter_try_charge(&memcg->memory, batch, &counter, false, NULL)) goto done_restock; if (do_memsw_account()) @@ -6026,7 +6027,8 @@ int __mem_cgroup_try_charge_swap(struct folio *folio) private_id = mem_cgroup_private_id_get(memcg, nr_pages); if (!mem_cgroup_private_id_is_root(private_id) && - !page_counter_try_charge(&memcg->swap, nr_pages, &counter)) { + !page_counter_try_charge(&memcg->swap, nr_pages, &counter, + false, NULL)) { memcg_memory_event(memcg, MEMCG_SWAP_MAX); memcg_memory_event(memcg, MEMCG_SWAP_FAIL); mem_cgroup_private_id_put(private_id, nr_pages); diff --git a/mm/page_counter.c b/mm/page_counter.c index 77624b00b5f94..e48ef37016c50 100644 --- a/mm/page_counter.c +++ b/mm/page_counter.c @@ -136,23 +136,76 @@ void page_counter_charge(struct page_counter *counter, unsigned long nr_pages) } } +/* + * Consume the cached charge if enough nr_pages are present, otherwise return + * failure. Also return failure for charge requests larger than + * PAGE_COUNTER_STOCK_BATCH or if the local lock is already taken. + */ +static bool page_counter_consume_stock(struct page_counter *counter, + unsigned long nr_pages) +{ + struct page_counter_stock_pcp __percpu *stock = counter->stock; + struct page_counter_stock_pcp *pcp_stock; + u8 stock_pages; + bool ret = false; + int i; + + if (nr_pages > PAGE_COUNTER_STOCK_BATCH || + !local_trylock(&stock->lock)) + return false; + + pcp_stock = this_cpu_ptr(stock); + for (i = 0; i < NR_PAGE_COUNTER_STOCK; i++) { + if (counter != READ_ONCE(pcp_stock->cached[i])) + continue; + + stock_pages = READ_ONCE(pcp_stock->nr_pages[i]); + if (stock_pages >= nr_pages) { + stock_pages -= nr_pages; + WRITE_ONCE(pcp_stock->nr_pages[i], stock_pages); + if (!stock_pages) { + css_put(counter->stock_css); + WRITE_ONCE(pcp_stock->cached[i], NULL); + } + ret = true; + } + break; + } + local_unlock(&stock->lock); + + return ret; +} + /** - * page_counter_try_charge - try to hierarchically charge pages + * page_counter_try_charge - try to hierarchically charge pages using stock * @counter: counter - * @nr_pages: number of pages to charge - * @fail: points first counter to hit its limit, if any + * @nr_pages: number of pages requested + * @fail: points to the first counter to hit its limit, if any + * @may_batch: whether a stock miss may trigger a batch charge + * @nr_charged: optional; set to the hierarchy charge size on success * - * Returns %true on success, or %false and @fail if the counter or one - * of its ancestors has hit its configured limit. + * Return: %true if the request was satisfied. A failed batch charge may update + * @fail before an exact retry succeeds. */ bool page_counter_try_charge(struct page_counter *counter, - unsigned long nr_pages, - struct page_counter **fail) + unsigned long nr_pages, struct page_counter **fail, + bool may_batch, unsigned long *nr_charged) { + unsigned long charge = nr_pages; struct page_counter *c; bool protection = track_protection(counter); bool track_failcnt = counter->track_failcnt; + if (counter->stock && may_batch) + charge = max(nr_pages, PAGE_COUNTER_STOCK_BATCH); + +retry: + if (counter->stock && page_counter_consume_stock(counter, nr_pages)) { + if (nr_charged) + *nr_charged = 0; + return true; + } + for (c = counter; c; c = c->parent) { long new; /* @@ -169,9 +222,9 @@ bool page_counter_try_charge(struct page_counter *counter, * we either see the new limit or the setter sees the * counter has changed and retries. */ - new = atomic_long_add_return(nr_pages, &c->usage); + new = atomic_long_add_return(charge, &c->usage); if (new > c->max) { - atomic_long_sub(nr_pages, &c->usage); + atomic_long_sub(charge, &c->usage); /* * This is racy, but we can live with some * inaccuracy in the failcnt which is only used @@ -192,11 +245,20 @@ bool page_counter_try_charge(struct page_counter *counter, WRITE_ONCE(c->watermark, new); } } + if (charge > nr_pages) + page_counter_refill_stock(counter, charge - nr_pages); + if (nr_charged) + *nr_charged = charge; return true; failed: for (c = counter; c != *fail; c = c->parent) - page_counter_cancel(c, nr_pages); + page_counter_cancel(c, charge); + + if (charge > nr_pages) { + charge = nr_pages; + goto retry; + } return false; } -- 2.53.0-Meta