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b=xPmsiXie4OcZUFHlMROAuktSHAy0q+wQlibAK2JCWTHsKT+MggqnGGI4ZHkr78fsF qwpRxYfO51EDhHLxGdpez6MxCew2ofAwAQGAIASG8xN43Ug0owad7b6gSQnQ5qpKeq yp/qX+OEINuNfJhP2Xlx4KsRkB44A0Zu9qSW30hw= Date: Sun, 1 Sep 2024 22:09:31 -0700 From: Andrew Morton To: Suren Baghdasaryan Cc: 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 Subject: Re: [PATCH v2 5/6] alloc_tag: make page allocation tag reference size configurable Message-Id: <20240901220931.53d3ad335ae9ac3fe7ef3928@linux-foundation.org> In-Reply-To: <20240902044128.664075-6-surenb@google.com> References: <20240902044128.664075-1-surenb@google.com> <20240902044128.664075-6-surenb@google.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: C18CEA0012 X-Stat-Signature: do4ua1jnoj5bu71qbrrng7a5fo3q8oh6 X-Rspamd-Server: rspam09 X-Rspam-User: X-HE-Tag: 1725253775-243670 X-HE-Meta: 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 BT8F3bTx L2/mfK86lOgFsdb4yHFXupTEpxY37D/EKva/1W3kGiI+wQ6Trxqh9atC7MlX+ttIS2y0JQKhhMwVgRZ+dlnRY/QlpvsK2FLUeUY/e9vV9Bqand/Ka0njMH4li+jGSOLOER5me+ch0yGjRHWFMlchELwj5uaJVhSV7HNjIp6eSq29RONtMOCRwlDXVH19/Ixp8CB5+x4BFsZtlQL1qp39VRIvDYpJ3Zw3cGWYsIse8Ype2cJF+v6GHMjszs66n5jDIMQs2vir/Wimka4ODfnkWoWv4901HXz1WrVbt15dmKevVuYXeUGlbnsW/UnJ/onxjT6QF 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: List-Subscribe: List-Unsubscribe: On Sun, 1 Sep 2024 21:41:27 -0700 Suren Baghdasaryan wrote: > Introduce CONFIG_PGALLOC_TAG_REF_BITS to control the size of the > page allocation tag references. When the size is configured to be > less than a direct pointer, the tags are searched using an index > stored as the tag reference. > > ... > > +config PGALLOC_TAG_REF_BITS > + int "Number of bits for page allocation tag reference (10-64)" > + range 10 64 > + default "64" > + depends on MEM_ALLOC_PROFILING > + help > + Number of bits used to encode a page allocation tag reference. > + > + Smaller number results in less memory overhead but limits the number of > + allocations which can be tagged (including allocations from modules). > + In other words, "we have no idea what's best for you, you're on your own". I pity our poor users. Can we at least tell them what they should look at to determine whether whatever random number they chose was helpful or harmful?