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[34.150.132.193]) by smtp.gmail.com with ESMTPSA id c15-20020ae9ed0f000000b006fafc111b12sm12716266qkg.83.2023.01.13.07.42.56 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 13 Jan 2023 07:42:56 -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 v3] mm/page_ext: Do not allocate space for page_ext->flags if not needed Date: Fri, 13 Jan 2023 15:42:53 +0000 Message-Id: <20230113154253.92480-1-pasha.tatashin@soleen.com> X-Mailer: git-send-email 2.39.0.314.g84b9a713c41-goog MIME-Version: 1.0 X-Spam-Status: No, score=-2.1 required=5.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,RCVD_IN_DNSWL_NONE, SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1754832104694180697?= X-GMAIL-MSGID: =?utf-8?q?1754923204390787995?= 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 comment before page_ext_operations that describes the field, 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 --- include/linux/page_ext.h | 19 +++++++++++++++++++ mm/page_ext.c | 14 ++++++++++++-- mm/page_owner.c | 1 + mm/page_table_check.c | 1 + 4 files changed, 33 insertions(+), 2 deletions(-) Changelog: v2: Fixed field name in page_owner.c that caused build error. v3: Added comment before page_ext_operations, removed check if need is null. diff --git a/include/linux/page_ext.h b/include/linux/page_ext.h index 22be4582faae..be0b465c7d78 100644 --- a/include/linux/page_ext.h +++ b/include/linux/page_ext.h @@ -7,15 +7,31 @@ #include struct pglist_data; + +/* + * Each Page Extension client must define page_ext_operations in + * page_ext_ops array. + * offset offset to the client's data within page_ext. Offset is returned 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 allocated. + * using_shared_ext_flags true when client is using shared page_ext->flags + * field. + */ struct page_ext_operations { size_t offset; size_t size; bool (*need)(void); void (*init)(void); + bool using_shared_ext_flags; }; #ifdef CONFIG_PAGE_EXTENSION +/* + * 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 +47,9 @@ 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..d14dbd44fa49 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 = { .need = need_page_idle, + .using_shared_ext_flags = true, }; #endif @@ -86,7 +87,7 @@ static struct page_ext_operations *page_ext_ops[] __initdata = { #endif }; -unsigned long page_ext_size = sizeof(struct page_ext); +unsigned long page_ext_size; 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 = false; for (i = 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]->using_shared_ext_flags) { + page_ext_size = sizeof(struct page_ext); + break; + } + } + } + + for (i = 0; i < entries; i++) { + if (page_ext_ops[i]->need()) { page_ext_ops[i]->offset = page_ext_size; page_ext_size += page_ext_ops[i]->size; need = true; 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 = { .size = sizeof(struct page_owner), .need = need_page_owner, .init = init_page_owner, + .using_shared_ext_flags = true, }; 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 = { .size = sizeof(struct page_table_check), .need = need_page_table_check, .init = init_page_table_check, + .using_shared_ext_flags = false, }; static struct page_table_check *get_page_table_check(struct page_ext *page_ext)