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[34.150.132.193]) by smtp.gmail.com with ESMTPSA id 195-20020a370ccc000000b007023fc46b64sm20688193qkm.113.2023.01.17.12.21.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Jan 2023 12:21:06 -0800 (PST) From: Pasha Tatashin To: pasha.tatashin@soleen.com, rppt@kernel.org, akpm@linux-foundation.org, mhocko@suse.com, vbabka@suse.cz, david@redhat.com, quic_charante@quicinc.com, lizhe.67@bytedance.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: [PATCH v4] mm/page_ext: Do not allocate space for page_ext->flags if not needed Date: Tue, 17 Jan 2023 20:21:03 +0000 Message-Id: <20230117202103.1412449-1-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" There is 8 byte page_ext->flags field allocated per page whenever CONFIG_PAGE_EXTENSION is enabled. However, not every user of page_ext uses flags. Therefore, check whether flags is needed at least by one user and if so allocate space for it. For example when page_table_check is enabled, on a machine with 128G of memory before the fix: [ 2.244288] allocated 536870912 bytes of page_ext after the fix: [ 2.160154] allocated 268435456 bytes of page_ext Also, add a kernel-doc comment before page_ext_operations that describes the fields, and remove check if need() is set, as that is now a required field. Signed-off-by: Pasha Tatashin Acked-by: Vlastimil Babka Acked-by: David Hildenbrand Acked-by: David Rientjes Reviewed-by: Mike Rapoport (IBM) --- include/linux/page_ext.h | 18 ++++++++++++++++++ mm/page_ext.c | 14 ++++++++++++-- mm/page_owner.c | 1 + mm/page_table_check.c | 1 + 4 files changed, 32 insertions(+), 2 deletions(-) Changelog: v4: Addressed comments from Mike Rapoport, added Acked-by's. v3: Added comment before page_ext_operations, removed check if need is null. v2: Fixed field name in page_owner.c that caused build error. diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h index 22be4582faae..67314f648aeb 100644 --- a/include/linux/page_ext.h +++ b/include/linux/page_ext.h @@ -7,15 +7,33 @@ #include =20 struct pglist_data; + +/** + * struct page_ext_operations - per page_ext client operations + * @offset: Offset to the client's data within page_ext. Offset is returne= d to + * the client by page_ext_init. + * @size: The size of the client data within page_ext. + * @need: Function that returns true if client requires page_ext. + * @init: (optional) Called to initialize client once page_exts are alloca= ted. + * @need_shared_flags: True when client is using shared page_ext->flags + * field. + * + * Each Page Extension client must define page_ext_operations in + * page_ext_ops array. + */ struct page_ext_operations { size_t offset; size_t size; bool (*need)(void); void (*init)(void); + bool need_shared_flags; }; =20 #ifdef CONFIG_PAGE_EXTENSION =20 +/* + * The page_ext_flags users must set need_shared_flags to true. + */ enum page_ext_flags { PAGE_EXT_OWNER, PAGE_EXT_OWNER_ALLOCATED, diff --git a/mm/page_ext.c b/mm/page_ext.c index 4ee522fd381c..e2c22ffdbb81 100644 --- a/mm/page_ext.c +++ b/mm/page_ext.c @@ -71,6 +71,7 @@ static bool need_page_idle(void) } static struct page_ext_operations page_idle_ops __initdata =3D { .need =3D need_page_idle, + .need_shared_flags =3D true, }; #endif =20 @@ -86,7 +87,7 @@ static struct page_ext_operations *page_ext_ops[] __initd= ata =3D { #endif }; =20 -unsigned long page_ext_size =3D sizeof(struct page_ext); +unsigned long page_ext_size; =20 static unsigned long total_usage; static struct page_ext *lookup_page_ext(const struct page *page); @@ -106,7 +107,16 @@ static bool __init invoke_need_callbacks(void) bool need =3D false; =20 for (i =3D 0; i < entries; i++) { - if (page_ext_ops[i]->need && page_ext_ops[i]->need()) { + if (page_ext_ops[i]->need()) { + if (page_ext_ops[i]->need_shared_flags) { + page_ext_size =3D sizeof(struct page_ext); + break; + } + } + } + + for (i =3D 0; i < entries; i++) { + if (page_ext_ops[i]->need()) { page_ext_ops[i]->offset =3D page_ext_size; page_ext_size +=3D page_ext_ops[i]->size; need =3D true; diff --git a/mm/page_owner.c b/mm/page_owner.c index 2d27f532df4c..f0553bedb39d 100644 --- a/mm/page_owner.c +++ b/mm/page_owner.c @@ -99,6 +99,7 @@ struct page_ext_operations page_owner_ops =3D { .size =3D sizeof(struct page_owner), .need =3D need_page_owner, .init =3D init_page_owner, + .need_shared_flags =3D true, }; =20 static inline struct page_owner *get_page_owner(struct page_ext *page_ext) diff --git a/mm/page_table_check.c b/mm/page_table_check.c index 93e633c1d587..25d8610c0042 100644 --- a/mm/page_table_check.c +++ b/mm/page_table_check.c @@ -45,6 +45,7 @@ struct page_ext_operations page_table_check_ops =3D { .size =3D sizeof(struct page_table_check), .need =3D need_page_table_check, .init =3D init_page_table_check, + .need_shared_flags =3D false, }; =20 static struct page_table_check *get_page_table_check(struct page_ext *page= _ext) --=20 2.39.0.314.g84b9a713c41-goog