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[34.150.132.193]) by smtp.gmail.com with ESMTPSA id u8-20020a05620a454800b006fc7302cf89sm11113288qkp.28.2023.01.12.07.33.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Jan 2023 07:33:50 -0800 (PST) From: Pasha Tatashin To: pasha.tatashin@soleen.com, 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 v2] mm/page_ext: Do not allocate space for page_ext->flags if not needed Date: Thu, 12 Jan 2023 15:33:48 +0000 Message-Id: <20230112153348.3202173-1-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 Signed-off-by: Pasha Tatashin --- include/linux/page_ext.h | 7 +++++++ mm/page_ext.c | 12 +++++++++++- mm/page_owner.c | 1 + mm/page_table_check.c | 1 + 4 files changed, 20 insertions(+), 1 deletion(-) Changelog: 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..29909e135052 100644 --- a/include/linux/page_ext.h +++ b/include/linux/page_ext.h @@ -12,10 +12,14 @@ struct page_ext_operations { size_t size; bool (*need)(void); void (*init)(void); + bool using_shared_ext_flags; }; =20 #ifdef CONFIG_PAGE_EXTENSION =20 +/* + * The page_ext_flags users must set using_shared_ext_flags to true. + */ enum page_ext_flags { PAGE_EXT_OWNER, PAGE_EXT_OWNER_ALLOCATED, @@ -31,6 +35,9 @@ enum page_ext_flags { * page_ext helps us add more information about the page. * All page_ext are allocated at boot or memory hotplug event, * then the page_ext for pfn always exists. + * Note: that if none of the users of page_ext is setting + * using_shared_ext_flags to true, the field cannot be used, + * as it will be overlapped with another data. */ struct page_ext { unsigned long flags; diff --git a/mm/page_ext.c b/mm/page_ext.c index 4ee522fd381c..7443a797b96b 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, + .using_shared_ext_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); @@ -105,6 +106,15 @@ static bool __init invoke_need_callbacks(void) int entries =3D ARRAY_SIZE(page_ext_ops); 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]->using_shared_ext_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]->need()) { page_ext_ops[i]->offset =3D page_ext_size; diff --git a/mm/page_owner.c b/mm/page_owner.c index 2d27f532df4c..1a62ab3fc00e 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, + .using_shared_ext_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..74cfe89d5f53 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, + .using_shared_ext_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