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charset="utf-8" From: Barry Song Anon large folios come from three places: 1. new allocated large folios in PF, they will call folio_add_new_anon_rmap= () for rmap; 2. a large folio is split into multiple lower-order large folios; 3. a large folio is migrated to a new large folio. In all above three counts, we increase nr_anon by 1; Anon large folios might go either because of be split or be put to free, in these cases, we reduce the count by 1. Folios that have been added to the swap cache but have not yet received an anon mapping won't be counted. This is consistent with the AnonPages statistics in /proc/meminfo. Signed-off-by: Barry Song Acked-by: David Hildenbrand --- Documentation/admin-guide/mm/transhuge.rst | 5 +++++ include/linux/huge_mm.h | 15 +++++++++++++-- mm/huge_memory.c | 13 ++++++++++--- mm/migrate.c | 4 ++++ mm/page_alloc.c | 5 ++++- mm/rmap.c | 1 + 6 files changed, 37 insertions(+), 6 deletions(-) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/adm= in-guide/mm/transhuge.rst index 058485daf186..9fdfb46e4560 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -527,6 +527,11 @@ split_deferred it would free up some memory. Pages on split queue are going to be split under memory pressure, if splitting is possible. =20 +nr_anon + the number of anon huge pages we have in the whole system. + These huge pages could be entirely mapped or have partially + unmapped/unused subpages. + As the system ages, allocating huge pages may be expensive as the system uses memory compaction to copy data around memory to free a huge page for use. There are some counters in ``/proc/vmstat`` to help diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 4c32058cacfe..2ee2971e4e10 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -126,6 +126,7 @@ enum mthp_stat_item { MTHP_STAT_SPLIT, MTHP_STAT_SPLIT_FAILED, MTHP_STAT_SPLIT_DEFERRED, + MTHP_STAT_NR_ANON, __MTHP_STAT_COUNT }; =20 @@ -136,14 +137,24 @@ struct mthp_stat { =20 DECLARE_PER_CPU(struct mthp_stat, mthp_stats); =20 -static inline void count_mthp_stat(int order, enum mthp_stat_item item) +static inline void mod_mthp_stat(int order, enum mthp_stat_item item, int = delta) { if (order <=3D 0 || order > PMD_ORDER) return; =20 - this_cpu_inc(mthp_stats.stats[order][item]); + this_cpu_add(mthp_stats.stats[order][item], delta); +} + +static inline void count_mthp_stat(int order, enum mthp_stat_item item) +{ + mod_mthp_stat(order, item, 1); } + #else +static inline void mod_mthp_stat(int order, enum mthp_stat_item item, int = delta) +{ +} + static inline void count_mthp_stat(int order, enum mthp_stat_item item) { } diff --git a/mm/huge_memory.c b/mm/huge_memory.c index d90d6e94a800..afb911789df8 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -596,6 +596,7 @@ DEFINE_MTHP_STAT_ATTR(shmem_fallback_charge, MTHP_STAT_= SHMEM_FALLBACK_CHARGE); DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT); DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED); DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED); +DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON); =20 static struct attribute *anon_stats_attrs[] =3D { &anon_fault_alloc_attr.attr, @@ -608,6 +609,7 @@ static struct attribute *anon_stats_attrs[] =3D { &split_attr.attr, &split_failed_attr.attr, &split_deferred_attr.attr, + &nr_anon_attr.attr, NULL, }; =20 @@ -3216,8 +3218,9 @@ int split_huge_page_to_list_to_order(struct page *pag= e, struct list_head *list, struct deferred_split *ds_queue =3D get_deferred_split_queue(folio); /* reset xarray order to new order after split */ XA_STATE_ORDER(xas, &folio->mapping->i_pages, folio->index, new_order); - struct anon_vma *anon_vma =3D NULL; + bool is_anon =3D folio_test_anon(folio); struct address_space *mapping =3D NULL; + struct anon_vma *anon_vma =3D NULL; int order =3D folio_order(folio); int extra_pins, ret; pgoff_t end; @@ -3229,7 +3232,7 @@ int split_huge_page_to_list_to_order(struct page *pag= e, struct list_head *list, if (new_order >=3D folio_order(folio)) return -EINVAL; =20 - if (folio_test_anon(folio)) { + if (is_anon) { /* order-1 is not supported for anonymous THP. */ if (new_order =3D=3D 1) { VM_WARN_ONCE(1, "Cannot split to order-1 folio"); @@ -3269,7 +3272,7 @@ int split_huge_page_to_list_to_order(struct page *pag= e, struct list_head *list, if (folio_test_writeback(folio)) return -EBUSY; =20 - if (folio_test_anon(folio)) { + if (is_anon) { /* * The caller does not necessarily hold an mmap_lock that would * prevent the anon_vma disappearing so we first we take a @@ -3382,6 +3385,10 @@ int split_huge_page_to_list_to_order(struct page *pa= ge, struct list_head *list, } } =20 + if (is_anon) { + mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); + mod_mthp_stat(new_order, MTHP_STAT_NR_ANON, 1 << (order - new_order)); + } __split_huge_page(page, list, end, new_order); ret =3D 0; } else { diff --git a/mm/migrate.c b/mm/migrate.c index 7e1267042a56..bde573ec2af8 100644 --- a/mm/migrate.c +++ b/mm/migrate.c @@ -423,6 +423,8 @@ static int __folio_migrate_mapping(struct address_space= *mapping, /* No turning back from here */ newfolio->index =3D folio->index; newfolio->mapping =3D folio->mapping; + if (folio_test_anon(folio) && folio_test_large(folio)) + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); if (folio_test_swapbacked(folio)) __folio_set_swapbacked(newfolio); =20 @@ -447,6 +449,8 @@ static int __folio_migrate_mapping(struct address_space= *mapping, */ newfolio->index =3D folio->index; newfolio->mapping =3D folio->mapping; + if (folio_test_anon(folio) && folio_test_large(folio)) + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_ANON, 1); folio_ref_add(newfolio, nr); /* add cache reference */ if (folio_test_swapbacked(folio)) { __folio_set_swapbacked(newfolio); diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 84a7154fde93..382c364d3efa 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1084,8 +1084,11 @@ __always_inline bool free_pages_prepare(struct page = *page, (page + i)->flags &=3D ~PAGE_FLAGS_CHECK_AT_PREP; } } - if (PageMappingFlags(page)) + if (PageMappingFlags(page)) { + if (PageAnon(page) && compound) + mod_mthp_stat(order, MTHP_STAT_NR_ANON, -1); 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Sun, 11 Aug 2024 15:50:08 -0700 (PDT) Received: from localhost.localdomain ([2407:7000:8942:5500:aaa1:59ff:fe57:eb97]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-710e5874ddcsm2822993b3a.28.2024.08.11.15.50.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sun, 11 Aug 2024 15:50:08 -0700 (PDT) From: Barry Song <21cnbao@gmail.com> To: akpm@linux-foundation.org, linux-mm@kvack.org Cc: baolin.wang@linux.alibaba.com, chrisl@kernel.org, david@redhat.com, hanchuanhua@oppo.com, ioworker0@gmail.com, kaleshsingh@google.com, kasong@tencent.com, linux-kernel@vger.kernel.org, ryan.roberts@arm.com, v-songbaohua@oppo.com, ziy@nvidia.com, yuanshuai@oppo.com Subject: [PATCH v2 2/2] mm: collect the number of anon large folios on split_deferred list Date: Mon, 12 Aug 2024 10:49:40 +1200 Message-Id: <20240811224940.39876-3-21cnbao@gmail.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20240811224940.39876-1-21cnbao@gmail.com> References: <20240811224940.39876-1-21cnbao@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Barry Song When an mTHP is added to the deferred_list, its partial pages are unused, leading to wasted memory and potentially increasing memory reclamation pressure. Detailing the specifics of how unmapping occurs is quite difficult and not that useful, so we adopt a simple approach: each time an mTHP enters the deferred_list, we increment the count by 1; whenever it leaves for any reason, we decrement the count by 1. Signed-off-by: Barry Song --- Documentation/admin-guide/mm/transhuge.rst | 5 +++++ include/linux/huge_mm.h | 1 + mm/huge_memory.c | 6 ++++++ 3 files changed, 12 insertions(+) diff --git a/Documentation/admin-guide/mm/transhuge.rst b/Documentation/adm= in-guide/mm/transhuge.rst index 9fdfb46e4560..7072469de8a8 100644 --- a/Documentation/admin-guide/mm/transhuge.rst +++ b/Documentation/admin-guide/mm/transhuge.rst @@ -532,6 +532,11 @@ nr_anon These huge pages could be entirely mapped or have partially unmapped/unused subpages. =20 +nr_split_deferred + the number of anon huge pages which have been partially unmapped + and put onto split queue. Those unmapped subpages are also unused + and temporarily wasting memory. + As the system ages, allocating huge pages may be expensive as the system uses memory compaction to copy data around memory to free a huge page for use. There are some counters in ``/proc/vmstat`` to help diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h index 2ee2971e4e10..1e2d5dbe82c5 100644 --- a/include/linux/huge_mm.h +++ b/include/linux/huge_mm.h @@ -127,6 +127,7 @@ enum mthp_stat_item { MTHP_STAT_SPLIT_FAILED, MTHP_STAT_SPLIT_DEFERRED, MTHP_STAT_NR_ANON, + MTHP_STAT_NR_SPLIT_DEFERRED, __MTHP_STAT_COUNT }; =20 diff --git a/mm/huge_memory.c b/mm/huge_memory.c index afb911789df8..1a12c011e2df 100644 --- a/mm/huge_memory.c +++ b/mm/huge_memory.c @@ -597,6 +597,7 @@ DEFINE_MTHP_STAT_ATTR(split, MTHP_STAT_SPLIT); DEFINE_MTHP_STAT_ATTR(split_failed, MTHP_STAT_SPLIT_FAILED); DEFINE_MTHP_STAT_ATTR(split_deferred, MTHP_STAT_SPLIT_DEFERRED); DEFINE_MTHP_STAT_ATTR(nr_anon, MTHP_STAT_NR_ANON); +DEFINE_MTHP_STAT_ATTR(nr_split_deferred, MTHP_STAT_NR_SPLIT_DEFERRED); =20 static struct attribute *anon_stats_attrs[] =3D { &anon_fault_alloc_attr.attr, @@ -610,6 +611,7 @@ static struct attribute *anon_stats_attrs[] =3D { &split_failed_attr.attr, &split_deferred_attr.attr, &nr_anon_attr.attr, + &nr_split_deferred_attr.attr, NULL, }; =20 @@ -3359,6 +3361,7 @@ int split_huge_page_to_list_to_order(struct page *pag= e, struct list_head *list, if (folio_order(folio) > 1 && !list_empty(&folio->_deferred_list)) { ds_queue->split_queue_len--; + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_SPLIT_DEFERRED, -1); /* * Reinitialize page_deferred_list after removing the * page from the split_queue, otherwise a subsequent @@ -3425,6 +3428,7 @@ void __folio_undo_large_rmappable(struct folio *folio) spin_lock_irqsave(&ds_queue->split_queue_lock, flags); if (!list_empty(&folio->_deferred_list)) { ds_queue->split_queue_len--; + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_SPLIT_DEFERRED, -1); list_del_init(&folio->_deferred_list); } spin_unlock_irqrestore(&ds_queue->split_queue_lock, flags); @@ -3466,6 +3470,7 @@ void deferred_split_folio(struct folio *folio) if (folio_test_pmd_mappable(folio)) count_vm_event(THP_DEFERRED_SPLIT_PAGE); count_mthp_stat(folio_order(folio), MTHP_STAT_SPLIT_DEFERRED); + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_SPLIT_DEFERRED, 1); list_add_tail(&folio->_deferred_list, &ds_queue->split_queue); ds_queue->split_queue_len++; #ifdef CONFIG_MEMCG @@ -3513,6 +3518,7 @@ static unsigned long deferred_split_scan(struct shrin= ker *shrink, list_move(&folio->_deferred_list, &list); } else { /* We lost race with folio_put() */ + mod_mthp_stat(folio_order(folio), MTHP_STAT_NR_SPLIT_DEFERRED, -1); list_del_init(&folio->_deferred_list); ds_queue->split_queue_len--; } --=20 2.34.1