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Tue, 17 Jan 2023 21:56:37 -0800 (PST) Date: Tue, 17 Jan 2023 21:56:36 -0800 (PST) From: David Rientjes To: Pasha Tatashin cc: 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: Re: [PATCH v4] mm/page_ext: Do not allocate space for page_ext->flags if not needed In-Reply-To: <20230117202103.1412449-1-pasha.tatashin@soleen.com> Message-ID: <59557eaf-7301-d142-4549-c3e196d011d5@google.com> References: <20230117202103.1412449-1-pasha.tatashin@soleen.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 8A53D2000E X-Stat-Signature: 5tnh798qzmtbkxcqgy78ekd6xu5e1b9i X-HE-Tag: 1674021399-245097 X-HE-Meta: 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 YpkPN8WY i1qS2986yiPGxZNi4FwOlC0bptdi3jnPGfNWDc7ey1inLSLe6ISstwO6vPCgtRiwWILXtSikrlL8zztu3OkXrK9wAhebMv7YYKjMwbeIBS9p1Bm7p7QxrptARcJyFxaSy1WQJIHpBwpFR8sE= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000013, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, 17 Jan 2023, 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 Acked-by: David Rientjes