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[176.36.0.241]) by smtp.gmail.com with ESMTPSA id vi13-20020a170907d40d00b00a3ce1bef210sm2263230ejc.28.2024.02.14.07.10.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 14 Feb 2024 07:10:54 -0800 (PST) Message-ID: <1f64dbe4a9eaa29a46e1985a5534fba14295ed9e.camel@gmail.com> Subject: Re: [PATCH v2 bpf-next 14/20] libbpf: Recognize __arena global varaibles. From: Eduard Zingerman To: Alexei Starovoitov Cc: bpf , Daniel Borkmann , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Tejun Heo , Barret Rhoden , Johannes Weiner , Lorenzo Stoakes , Andrew Morton , Uladzislau Rezki , Christoph Hellwig , linux-mm , Kernel Team Date: Wed, 14 Feb 2024 17:10:52 +0200 In-Reply-To: References: <20240209040608.98927-1-alexei.starovoitov@gmail.com> <20240209040608.98927-15-alexei.starovoitov@gmail.com> Autocrypt: addr=eddyz87@gmail.com; prefer-encrypt=mutual; keydata=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 A+T7mluw nYzhLWGcczc6J71q1Dje0l5vIPaSFOgwmWD4DA+WvuxM/shH4rtWeodbv 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 IYKvsh7s t1iq+gsfnXbPz5AnS598ScZI1oP7OrPSFJkt/z4acEbOQDQs8aUqrd46PV jsdqGvKnXZxzylux29UTNby4jTlz9pNJM+wPrDRmGfchLDUmf6CffaUYCbu4FiId+9+dcTCDvxbABRy1C3OJ8QY7cxfJ+pEZW18fRJ0XCl/fiV/ecAOfB3HsqgTzAn555h0rkFgay0hAvMU/mAW/CFNSIxV397zm749ZNLA0L2dMy1AKuOqH+/B+/ImBfJMDjmdyJQ8WU/OFRuGLdqOd2oZrA1iuPIa+yUYyZkaZfz/emQwpIL1+Q4p1R/OplA4yc301AqruXXUcVDbEB+joHW3hy5FwK5t5OwTKatrSJBkydSF9zdXy98fYzGniRyRA65P0Ix/8J3BYB4edY2/w0Ip/mdYsYQljBY0A== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.50.3 MIME-Version: 1.0 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 11C43C000D X-Stat-Signature: 85rukp773m3m31jsyk7r1wr5tnukaajd X-Rspam-User: X-HE-Tag: 1707923456-16640 X-HE-Meta: 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 QLVUya7R 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000041, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, 2024-02-13 at 17:02 -0800, Alexei Starovoitov wrote: [...] > > First is regarding initialization data. > > In bpf_object__init_internal_map() the amount of bpf_map_mmap_sz(map) > > bytes is mmaped and only data_sz bytes are copied, > > then bpf_map_mmap_sz(map) bytes are copied in bpf_object__create_maps()= . > > Is Linux/libc smart enough to skip action on pages which were mmaped bu= t > > never touched? >=20 > kernel gives zeroed out pages to user space. > So it's ok to mmap a page, copy data_sz bytes into it > and later copy the full page from one addr to another. > No garbage copy. > In this case there will be data by llvm construction of ".arena.1" > It looks to me that even .bss-like __arena vars have zero-s in data > and non-zero data_sz. I was actually worried about second memcpy increasing RSS unnecessarily, but I missed that internal map does: def->max_entries =3D roundup(data_sz, page_sz) / page_sz; So that is not an issue as bpf_map_mmap_sz() for internal map is proportional to data_sz, not full arena. Sorry for the noise.