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Mon, 22 Apr 2024 07:56:20 +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 +NSwLyQYJmb/cgAAD6G6ig (envelope-from ); Mon, 22 Apr 2024 07:56:20 +0000 Message-ID: <1d795e22-cbcd-4107-978e-96bb459629a4@suse.cz> Date: Mon, 22 Apr 2024 09:56:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/2] slub: introduce count_partial_free_approx() Content-Language: en-US To: Jianfeng Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: cl@linux.com, akpm@linux-foundation.org, penberg@kernel.org, rientjes@google.com References: <20240419175611.47413-1-jianfeng.w.wang@oracle.com> 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: <20240419175611.47413-1-jianfeng.w.wang@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: AB7A840020 X-Stat-Signature: br1mgctsy5he13wwj64cqayn5atoc693 X-Rspam-User: X-HE-Tag: 1713772583-270266 X-HE-Meta: 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 f/3HMWvx aP1GKjRqF+0joypA39yTDNOjE7Y01FubH6WnB8OKq1gr44cfq7q3CM2uSUYJZBqdo663BqZFTBoi/Um1wu+K1vT6IrImekwQOitjm9/4kAwbUFfGioAMGc2Kdm+7pYku5m9EdTwn9wmVrM3TinrBt1fHpezvXANSK7S1AS+vbmtPV1KNIbvTxCc3up0SY/oexJDRxr8qgl4DXLiCca8Z/xSjPjNvTgHN19qOW2cp//B1yWR5GUb/DX8HMZ7ssGwmw/qv6CNtJyFX+uA0payNNP2NXj7AFGL2NcKW9++OW2dZgWK4DJfjNu5Js8bwMCyLk4b1bzNUM9d3a8z1v0PweLkiL6FUTyxTOBTUd+0NNP/lv5ws0QG2a7sySq1k1JgAaJMJCFhmqFC9ylgk= 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 4/19/24 7:56 PM, Jianfeng Wang wrote: > This patch fixes a known issue in get_slabinfo() which relies on > count_partial() to get the exact count of free objects in a > kmem_cache_node's partial list. For some slubs, their partial lists > can be extremely long. Currently, count_partial() traverses a partial > list to get the exact count of objects. This process may take a long > time, during which slab allocations are blocked and IRQs are disabled. > In production, even NMI watchdog can be triggered due to this matter. > > The proposed fix is to limit the number of slabs to scan and output an > approximated count for a long partial list. The v1 patch counts N slabs > from the list's head and then uses it to estimate the total object > count in the list. As suggested by Vlastimil, the v2 patch uses an > alternative, i.e., counting N/2 from the list's head and tail, produces > a more accurate approximation after the partial list is sorted by > kmem_cache_shrink(). In this version, the implementation is moved to a > new function count_partial_free_approx(). count_partial() is still used > in sysfs for users who still want the exact object count. Added to slab/for-next, thanks! > > --- > Changes since v2 [2] > - Introduce count_partial_free_approx() and keep count_partial() > - Use count_partial_free_approx() in get_slabinfo() and slab_out_of_memory() > > Changes since v1 [1] > - Update the approximation method by counting from the list's head and tail > - Cap the approximation by the total object count > - Update the commit message to add benchmark results and explain the choice > > [1] https://lore.kernel.org/linux-mm/20240411164023.99368-1-jianfeng.w.wang@oracle.com/ > [2] https://lore.kernel.org/linux-mm/20240417185938.5237-2-jianfeng.w.wang@oracle.com/ > > Thanks, > --Jianfeng > > Jianfeng Wang (2): > slub: introduce count_partial_free_approx() > slub: use count_partial_free_approx() in slab_out_of_memory() > > mm/slub.c | 41 +++++++++++++++++++++++++++++++++++++++-- > 1 file changed, 39 insertions(+), 2 deletions(-) >