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Tue, 26 Nov 2024 07:32:25 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id eB3uHYl5RWfHYQAAD6G6ig (envelope-from ); Tue, 26 Nov 2024 07:32:25 +0000 Message-ID: <8b10446a-16bc-4967-b03c-7be577671dab@suse.cz> Date: Tue, 26 Nov 2024 08:32:25 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] mm: mmap_lock: optimize mmap_lock tracepoints To: Shakeel Butt , Andrew Morton Cc: Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , Axel Rasmussen , Steven Rostedt , Suren Baghdasaryan , Matthew Wilcox , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team References: <20241125171617.113892-1-shakeel.butt@linux.dev> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <20241125171617.113892-1-shakeel.butt@linux.dev> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 2E4291C000D X-Stat-Signature: bhcuei887ya7s3xko9tfagkpyx9wyrxx X-HE-Tag: 1732606341-65981 X-HE-Meta: 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 MF4EAkkx BwOKxogA3ekB/ASh8mKrzMh93JpPmw1BFhtpi8i3pPDHY2Kflam5Gut356KF4Z7zFD/e1GLU0NNTd7qKuKOD6hy13Xk9A+1ZSliPy5qWG72/Q7Jz3jbD5tDneYgRHaCvv3ffjQNVqME7Bw3EkezdIhReXSyjKBJkqOue2YYTkmWc3V71vHZfLziXWaby8cMGsIO5yw35mH9dtroQyR/GQ5U011I1wZ+c5xsNpCMVAe6rYMwsyqLanGNRM/2XU1EpSYH9F6G+7Bi3Gtif0ADpxR0PuWY7BHJkeaJrXOTRQWnc3oalP1oyJCOMsBFF5bXKOBoCvMziOHSqR2ldgCAZLr12DfA== 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 11/25/24 18:16, Shakeel Butt wrote: > We are starting to deploy mmap_lock tracepoint monitoring across our > fleet and the early results showed that these tracepoints are consuming > significant amount of CPUs in kernfs_path_from_node when enabled. > > It seems like the kernel is trying to resolve the cgroup path in the > fast path of the locking code path when the tracepoints are enabled. In > addition for some application their metrics are regressing when > monitoring is enabled. > > The cgroup path resolution can be slow and should not be done in the > fast path. Most userspace tools, like bpftrace, provides functionality > to get the cgroup path from cgroup id, so let's just trace the cgroup > id and the users can use better tools to get the path in the slow path. > > Signed-off-by: Shakeel Butt Acked-by: Vlastimil Babka