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AJvYcCWn8MgQgJ/RVh6beg9EVpkce01Dt9yEiZilzUBTfPt8nwuCs5R3/mmud8/fP7sYcT42Bb81cowMww==@kvack.org X-Gm-Message-State: AOJu0YwrkMdcY3VF3hIA51rzQ3da/jd6VZ3KlKFCDFJ2nAEYe+5LcmnF uHalb8A8Q1I/tjy44KdG3WVpSiK2/DaRAS85yP89bkwtua3uU31V8BuAcluVHn9qFMTT323vzaZ dhrzNVUEPyC8U06R+9IEsgrqs7IJJjKhKSeyy X-Google-Smtp-Source: AGHT+IF3LTkRo2bNnzsq5dT0NEdsT3wmUih6L0PdgKsa4EEm9X0C1vz+srf2kxl0ec7RLeunLrfhzidYV/TpVSBkxmQ= X-Received: by 2002:a17:907:e6cc:b0:a86:94e2:2a47 with SMTP id a640c23a62f3a-a99e3b5a86dmr831600866b.15.1728949758341; Mon, 14 Oct 2024 16:49:18 -0700 (PDT) MIME-Version: 1.0 References: <20241014203646.1952505-1-surenb@google.com> <20241014203646.1952505-6-surenb@google.com> In-Reply-To: <20241014203646.1952505-6-surenb@google.com> From: Yosry Ahmed Date: Mon, 14 Oct 2024 16:48:41 -0700 Message-ID: Subject: Re: [PATCH v3 5/5] alloc_tag: config to store page allocation tag refs in page flags To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, kent.overstreet@linux.dev, corbet@lwn.net, arnd@arndb.de, mcgrof@kernel.org, rppt@kernel.org, paulmck@kernel.org, thuth@redhat.com, tglx@linutronix.de, bp@alien8.de, xiongwei.song@windriver.com, ardb@kernel.org, david@redhat.com, vbabka@suse.cz, mhocko@suse.com, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, pasha.tatashin@soleen.com, souravpanda@google.com, keescook@chromium.org, dennis@kernel.org, jhubbard@nvidia.com, yuzhao@google.com, vvvvvv@google.com, rostedt@goodmis.org, iamjoonsoo.kim@lge.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-modules@vger.kernel.org, kernel-team@android.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6B89410000D X-Stat-Signature: io9hb6ghc8ns4fiz7e83dzgztzjfce1p X-HE-Tag: 1728949752-184926 X-HE-Meta: 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 2nintq7Z dKeDUCtG7HLyHpDx6dU7l6aSNBuWoHSTii3CvKS3sTzsGEk61vfRx7sqHfZ9W9ySM60/Duvl/bUdH6TeSkGH4G5dafUn1GgOScjgkAep62tfv/adXJj3GQId9212IxAD4KouzseeGM/WwE7kePE1/YFy8tHtBKR4Hx7WPkJ0nUbKvbIYLUlkil51N8ziDo9n8RwaHIZ74PgE18kZmhfv0eGq4SHf6CAnycETEjO+nCIAT9nRDJVrrmkxXKaZrNhxV13/SQDmjnvgq2d8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.002743, 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 Mon, Oct 14, 2024 at 1:37=E2=80=AFPM Suren Baghdasaryan wrote: > > Add CONFIG_PGALLOC_TAG_USE_PAGEFLAGS to store allocation tag > references directly in the page flags. This eliminates memory > overhead caused by page_ext and results in better performance > for page allocations. > If the number of available page flag bits is insufficient to > address all kernel allocations, profiling falls back to using > page extensions with an appropriate warning to disable this > config. > If dynamically loaded modules add enough tags that they can't > be addressed anymore with available page flag bits, memory > profiling gets disabled and a warning is issued. Just curious, why do we need a config option? If there are enough bits in page flags, why not use them automatically or fallback to page_ext otherwise? Is the reason that dynamically loadable modules, where the user may know in advance that the page flags won't be enough with the modules loaded?