From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 2CAF2C7EE3A for ; Thu, 29 Aug 2024 08:43:06 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 73FDB8D0002; Thu, 29 Aug 2024 04:43:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6EF4F6B00BA; Thu, 29 Aug 2024 04:43:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5B7298D0002; Thu, 29 Aug 2024 04:43:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 3D86C6B00B5 for ; Thu, 29 Aug 2024 04:43:05 -0400 (EDT) Received: from smtpin24.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id D8C5AC031C for ; Thu, 29 Aug 2024 08:43:04 +0000 (UTC) X-FDA: 82504643088.24.A11E55A Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf01.hostedemail.com (Postfix) with ESMTP id 5D42740014 for ; Thu, 29 Aug 2024 08:43:02 +0000 (UTC) Authentication-Results: imf01.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBG8Jv3M; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=JIScSlPw; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBG8Jv3M; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=JIScSlPw; dmarc=none; spf=pass (imf01.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1724920883; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=xGgKB94X18u4BWVG/408x1i1MPxhgGHHEk6ZLEVibLI=; b=wGOSv+Mzwttm8b+b/8OlquhZ3w/tNrBDzNK3FNX3Tu7TYEbrWe0wgOCtt+Pfc13IXghotg sTzNXwG8L6pW4YZwgpFR54FnWJ2JiIarpSoGXGbKZ4Vfmd4g4DnZjPYBuo0FGmhz2kz/dJ 1oMe6GYIp223ylLRCoOSZ86U9XrMx9o= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1724920883; a=rsa-sha256; cv=none; b=yil1gnZY7c8bBFp/tvtDVQO7PbFxxrjYln0Lj7ZhDX/FKB6DYuxyxgfa823UbEg3/APYYl 19CAav8U80l4B8/zQ0iB+LQFyT+aaSJHJWv+jIORj8NNdhUBM7Nu9ZpTmMC/J/vzafgB8h R6qE5b0D8rl/TKFX5lF5vlOzq5dO/9c= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBG8Jv3M; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=JIScSlPw; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=eBG8Jv3M; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=JIScSlPw; dmarc=none; spf=pass (imf01.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [IPv6:2a07:de40:b281:104:10:150:64:97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by smtp-out1.suse.de (Postfix) with ESMTPS id 7BC0421B27; Thu, 29 Aug 2024 08:43:00 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1724920980; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=xGgKB94X18u4BWVG/408x1i1MPxhgGHHEk6ZLEVibLI=; b=eBG8Jv3M8zWK50aRJ+07McnvxLmqHX9gQCHhzM3EW1HSeK0j9VNaphjXCGKwbuXUCwe2YR XfjuYEsa7kd6hFa1TANOgMx/aAorBuolh+QJ8gy4GX0eTN2ttP5juIuLb4PlTgUNYuIoWf oFmNAIg8yCbdseP0UIl7wtXoxozuUpk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1724920980; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=xGgKB94X18u4BWVG/408x1i1MPxhgGHHEk6ZLEVibLI=; b=JIScSlPw3n+8qZI1MQ4Nb3bZqQkiLRdOucmgrneyYdQoKkFTrAHAzlF1Gu9WDw6aff7Cx5 AAia/fGJne2WXtAA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1724920980; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=xGgKB94X18u4BWVG/408x1i1MPxhgGHHEk6ZLEVibLI=; b=eBG8Jv3M8zWK50aRJ+07McnvxLmqHX9gQCHhzM3EW1HSeK0j9VNaphjXCGKwbuXUCwe2YR XfjuYEsa7kd6hFa1TANOgMx/aAorBuolh+QJ8gy4GX0eTN2ttP5juIuLb4PlTgUNYuIoWf oFmNAIg8yCbdseP0UIl7wtXoxozuUpk= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1724920980; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=xGgKB94X18u4BWVG/408x1i1MPxhgGHHEk6ZLEVibLI=; b=JIScSlPw3n+8qZI1MQ4Nb3bZqQkiLRdOucmgrneyYdQoKkFTrAHAzlF1Gu9WDw6aff7Cx5 AAia/fGJne2WXtAA== Received: from imap1.dmz-prg2.suse.org (localhost [127.0.0.1]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by imap1.dmz-prg2.suse.org (Postfix) with ESMTPS id 55AEF13408; Thu, 29 Aug 2024 08:43:00 +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 MBCLFJQ00GaCYwAAD6G6ig (envelope-from ); Thu, 29 Aug 2024 08:43:00 +0000 Message-ID: <22e28cb5-4834-4a21-8ebb-e4e53259014c@suse.cz> Date: Thu, 29 Aug 2024 10:42:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2] memcg: add charging of already allocated slab objects Content-Language: en-US To: Yosry Ahmed , Shakeel Butt Cc: Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , David Rientjes , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Eric Dumazet , "David S . Miller" , Jakub Kicinski , Paolo Abeni , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Meta kernel team , cgroups@vger.kernel.org, netdev@vger.kernel.org References: <20240827235228.1591842-1-shakeel.butt@linux.dev> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5D42740014 X-Stat-Signature: 9reror7cb3h8rggn8kx35tis8eerttgu X-Rspam-User: X-HE-Tag: 1724920982-233434 X-HE-Meta: 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 rSH/cn5E tUMAg0Naq4w6cCfHrdyjvh1b8INDRa0gws4GKk214kIB0eFBp6Yc2wCGgtStVcwen2gRu2VIygPlG8tVr7HDRlGtI4YZto93LbDPPJcxs6gzE9ZsUtjNMwqS4sWn3NyxZ2VFL/IRHziYN3v1zfwEkkt8WXw3o8hnQ4R631t+1vb4m7fpfjFqshYEg1wmhxmPePVmoduTMQ7vL5mx1PEoJdN5IYnnZitZHfniIDyFBSwNeubdmwcYPzn5yEKHVvyRsCvGQRqZKqbqn8QJUyjcPn49/VIEHFEhLlGkUNCOvd8O8x263Zw5GdS6Gh4/0hZNZLB8CkQyH+Kqe0T8+v0GRPpu/pmVQRIEEyslRKk3FEES6vvRqS25833ADP96DXcP9Kng432g5QJHITQP490+NFne+UcUS2T5xYVoH 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 8/29/24 02:49, Yosry Ahmed wrote: > On Wed, Aug 28, 2024 at 5:20 PM Shakeel Butt wrote: >> >> On Wed, Aug 28, 2024 at 04:25:30PM GMT, Yosry Ahmed wrote: >> > On Tue, Aug 27, 2024 at 4:52 PM Shakeel Butt wrote: >> > > >> [...] >> > > + >> > > + /* Ignore KMALLOC_NORMAL cache to avoid circular dependency. */ >> > > + if ((s->flags & KMALLOC_TYPE) == SLAB_KMALLOC) >> > > + return true; >> > >> > Taking a step back here, why do we need this? Which circular >> > dependency are we avoiding here? >> >> commit 494c1dfe855ec1f70f89552fce5eadf4a1717552 >> Author: Waiman Long >> Date: Mon Jun 28 19:37:38 2021 -0700 >> >> mm: memcg/slab: create a new set of kmalloc-cg- caches >> >> There are currently two problems in the way the objcg pointer array >> (memcg_data) in the page structure is being allocated and freed. >> >> On its allocation, it is possible that the allocated objcg pointer >> array comes from the same slab that requires memory accounting. If this >> happens, the slab will never become empty again as there is at least >> one object left (the obj_cgroup array) in the slab. >> >> When it is freed, the objcg pointer array object may be the last one >> in its slab and hence causes kfree() to be called again. With the >> right workload, the slab cache may be set up in a way that allows the >> recursive kfree() calling loop to nest deep enough to cause a kernel >> stack overflow and panic the system. >> ... > > Thanks for the reference, this makes sense. Another reason is memory savings, if we have a small subset of objects in KMALLOC_NORMAL caches accounted, there might be e.g. one vector per a slab just to account on object while the rest is unaccounted. Separating between kmalloc and kmalloc-cg caches keeps the former with no vectors and the latter with fully used vectors. > Wouldn't it be easier to special case the specific slab cache used for > the objcg vector or use a dedicated cache for it instead of using > kmalloc caches to begin with? The problem is the vector isn't a fixed size, it depends on how many objects a particular slab (not even a particular cache) has. > Anyway, I am fine with any approach you and/or the slab maintainers > prefer, as long as we make things clear. If you keep the following > approach as-is, please expand the comment or refer to the commit you > just referenced. > > Personally, I prefer either explicitly special casing the slab cache > used for the objcgs vector, explicitly tagging KMALLOC_NORMAL > allocations, or having a dedicated documented helper that finds the > slab cache kmalloc type (if any) or checks if it is a KMALLOC_NORMAL > cache. A helper to check is_kmalloc_normal() would be better than defining KMALLOC_TYPE and using it directly, yes. We don't need to handle any other types now until anyone needs those.