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b=1qF4aD/hieYUCwc61HpYfOJSBPUv1Yqk6NoPwArkZig80qt9HoxzSMm7q71whm3Cr pflZtKoVBdNtUYUMMIMAvWVAwvTDQDUtehzRHbcnMSaUqn4J4Pe5stp4mE3lAC7U9v fKRYxAjKmWzezttvCgFwJaKKTUJMNjInQnOUdSkY= Date: Tue, 23 Jul 2024 23:46:00 -0700 From: Andrew Morton To: Pasha Tatashin Cc: jpoimboe@kernel.org, kent.overstreet@linux.dev, peterz@infradead.org, nphamcs@gmail.com, cerasuolodomenico@gmail.com, surenb@google.com, lizhijian@fujitsu.com, willy@infradead.org, shakeel.butt@linux.dev, vbabka@suse.cz, ziy@nvidia.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v4] vmstat: Kernel stack usage histogram Message-Id: <20240723234600.d05817293ec1eb2d4ad87be7@linux-foundation.org> In-Reply-To: <20240718202611.1695164-1-pasha.tatashin@soleen.com> References: <20240718202611.1695164-1-pasha.tatashin@soleen.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-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 6F11DA001A X-Stat-Signature: 6h93od73iu9bed7jxcn7b7rs4ttuwbbr X-HE-Tag: 1721803565-461113 X-HE-Meta: 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 36OoMGhr iHrVricalWlZ1GfS/PxSe3z9WwnF/G/A8LEzNEQlxEANbMBNDfcbawCKNAKlIdHfdx4nFw9g9hYgBKfq9uNCd+t22zHKMxYawJbhVYbBJEDlZpMle+2PBqlKxI+KyPFli9MQWJwPk+bueSLI01BBDm4AtzHKkBmueHLxrmXhHNDBHa9GoYkqhNN6Kjz+yduXPfYmGKai+T8GRxB5BhEc96Rk+Gml0Wbo7LIlrtt+ZZi+EBw/bduu4ixen8jfVeK53DWNPRBZgAojisFFhK7yInmswD+U4FLRmfAMJ 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 Thu, 18 Jul 2024 20:26:11 +0000 Pasha Tatashin wrote: > As part of the dynamic kernel stack project, we need to know the amount > of data that can be saved by reducing the default kernel stack size [1]. > > Provide a kernel stack usage histogram to aid in optimizing kernel stack > sizes and minimizing memory waste in large-scale environments. The > histogram divides stack usage into power-of-two buckets and reports the > results in /proc/vmstat. This information is especially valuable in > environments with millions of machines, where even small optimizations > can have a significant impact. x86_64 allmodconfig: In file included from : In function 'init_memcg_events', inlined from 'mem_cgroup_css_alloc' at mm/memcontrol.c:3616:3: ././include/linux/compiler_types.h:510:45: error: call to '__compiletime_assert_2305' declared with attribute error: BUILD_BUG_ON failed: NR_VM_EVENT_ITEMS >= S8_MAX 510 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^ ././include/linux/compiler_types.h:491:25: note: in definition of macro '__compiletime_assert' 491 | prefix ## suffix(); \ | ^~~~~~ ././include/linux/compiler_types.h:510:9: note: in expansion of macro '_compiletime_assert' 510 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__) | ^~~~~~~~~~~~~~~~~~~ ./include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert' 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg) | ^~~~~~~~~~~~~~~~~~ ./include/linux/build_bug.h:50:9: note: in expansion of macro 'BUILD_BUG_ON_MSG' 50 | BUILD_BUG_ON_MSG(condition, "BUILD_BUG_ON failed: " #condition) | ^~~~~~~~~~~~~~~~ mm/memcontrol.c:444:9: note: in expansion of macro 'BUILD_BUG_ON' 444 | BUILD_BUG_ON(NR_VM_EVENT_ITEMS >= S8_MAX); | ^~~~~~~~~~~~ This looks legitimate - is it time to switch to int16_t?