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bh=Li0EPMHtSKQ7wkJMyWtwCEqB+BQ3FhQiHQm1YGZAm0g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LP7iYAc68vJ7CcKxOti6Tiv/s+840HikPidjdAwxKpYBkpZd0BWIBTNb4B+odqgGN TQZHAxW0MeTrpejtn6CqQeZXjy+y6HOHxNU8W4e2Id1lbaD0mxP/J8uCegqpPH6wWp etuqQXalH+jjMqf7MdzprNI+F6FVZLCf2UM5J02lkFmf2BXlkzGP1cuvmJknMLsv30 gl2EQmp0Xnww9iEjSh7ACJZaWpJBcUV9VrfANpbwFdm6KSeYUPcbOLs5njPA5RBSnC TkIudFQwRjBZVqpaCkpgShlj8wf2Mg0Nf1YU/frrvGe6+XNdbbnIIEKtLFGWTLCx6t QprStRxqEI6lA== Date: Wed, 18 Jan 2023 07:53:32 +0200 From: Mike Rapoport To: Pasha Tatashin Cc: 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: Re: [PATCH v4] mm/page_ext: Do not allocate space for page_ext->flags if not needed Message-ID: References: <20230117202103.1412449-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230117202103.1412449-1-pasha.tatashin@soleen.com> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: BF85E80004 X-Stat-Signature: qdaw1mqi9b877biph171mm1n1fr5o5kx X-Rspam-User: X-HE-Tag: 1674021226-714201 X-HE-Meta: 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 PqSJJnam VRG6GfCNboGthPe+rwXYEtOzro748L5aKIJzSdY5AUQ7FrZuJ0t7LoRKWKsNfYvKHc/ofLPySXuCQp/o= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 17, 2023 at 08:21:03PM +0000, Pasha Tatashin wrote: > 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 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 > > struct pglist_data; > + > +/** > + * struct page_ext_operations - per page_ext client operations > + * @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. > + * @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; > }; > > #ifdef CONFIG_PAGE_EXTENSION > > +/* > + * 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 = { > .need = need_page_idle, > + .need_shared_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]->need_shared_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..f0553bedb39d 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, > + .need_shared_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..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 = { > .size = sizeof(struct page_table_check), > .need = need_page_table_check, > .init = init_page_table_check, > + .need_shared_flags = false, > }; > > static struct page_table_check *get_page_table_check(struct page_ext *page_ext) > -- > 2.39.0.314.g84b9a713c41-goog > -- Sincerely yours, Mike.