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 F1337D462B2 for ; Wed, 13 Nov 2024 14:45:29 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 670BD6B00B4; Wed, 13 Nov 2024 09:45:29 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6219B6B00B9; Wed, 13 Nov 2024 09:45:29 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 499536B00BB; Wed, 13 Nov 2024 09:45:29 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 2C1496B00B4 for ; Wed, 13 Nov 2024 09:45:29 -0500 (EST) Received: from smtpin05.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay10.hostedemail.com (Postfix) with ESMTP id BB9B6C0ADA for ; Wed, 13 Nov 2024 14:45:28 +0000 (UTC) X-FDA: 82781344128.05.5002E70 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) by imf07.hostedemail.com (Postfix) with ESMTP id B09B440026 for ; Wed, 13 Nov 2024 14:44:25 +0000 (UTC) Authentication-Results: imf07.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=WPSeJB9G; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=T8nB2loc; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=WPSeJB9G; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=T8nB2loc; dmarc=none; spf=pass (imf07.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 as permitted sender) smtp.mailfrom=vbabka@suse.cz ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1731508949; a=rsa-sha256; cv=none; b=sg4CH4pKw5GCwp1sEjWSfSwDvwkBrOmaiF4rwcHTNCdotUMDHoyQOL3OEIaIzZExw1abUs pA6ZW+ldsv74lx/32R1i5uedLig/b+CIbWUkBorJW1RAlWdZ330D5qxGxH+oTYWCIFizim uRXjbNLUxIXXYQ7d7uKfx/ZE/Qa/Yns= ARC-Authentication-Results: i=1; imf07.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=WPSeJB9G; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=T8nB2loc; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=WPSeJB9G; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=T8nB2loc; dmarc=none; spf=pass (imf07.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 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=1731508949; 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=E4rFv1ZA/uRDxlvEMPbfDFWN0AihJbSYcqJdWCdPI+g=; b=ZZcFyen6jsKdj4M+n+I7l+3PZmZazkpphdb/3jPvjK+7HMqNltEmir6E2SzY6TlsOGqAUU LopGo9q5Vh4Ub32fW2xnzJDwsn2maiKhg4zSB1Y/i2sZkhYSzOh7bMcBSA9GbAnEEa6D2I iz/8V9ZykJQXAboanO+M9SCq6+A//ZU= Received: from imap1.dmz-prg2.suse.org (unknown [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-out2.suse.de (Postfix) with ESMTPS id 833171F37C; Wed, 13 Nov 2024 14:45:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1731509124; 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=E4rFv1ZA/uRDxlvEMPbfDFWN0AihJbSYcqJdWCdPI+g=; b=WPSeJB9Gn4q06cF+af07FXtVHNypWsyU9n6sY6X6iDR3GSgmSIOBcJm/IUSYadhBa+wdwg PGoOIdKg9NCQGGPgcGEU3O6HZWXMyDEJ2AtIrgpG3rwnzoEzhp4F4XGyeH+Nuj+2IXeh+/ YVWD2Ty1KP3H2ghplfiTMIu7k/AzwAw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1731509124; 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=E4rFv1ZA/uRDxlvEMPbfDFWN0AihJbSYcqJdWCdPI+g=; b=T8nB2locELHtG6a60QtOlzpRXM5w+PgUfW/jhNBB9RSxKLzsr6EQ+IaIORCRNANhgbOMfh o+80FtuWgBLKODAA== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1731509124; 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=E4rFv1ZA/uRDxlvEMPbfDFWN0AihJbSYcqJdWCdPI+g=; b=WPSeJB9Gn4q06cF+af07FXtVHNypWsyU9n6sY6X6iDR3GSgmSIOBcJm/IUSYadhBa+wdwg PGoOIdKg9NCQGGPgcGEU3O6HZWXMyDEJ2AtIrgpG3rwnzoEzhp4F4XGyeH+Nuj+2IXeh+/ YVWD2Ty1KP3H2ghplfiTMIu7k/AzwAw= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1731509124; 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=E4rFv1ZA/uRDxlvEMPbfDFWN0AihJbSYcqJdWCdPI+g=; b=T8nB2locELHtG6a60QtOlzpRXM5w+PgUfW/jhNBB9RSxKLzsr6EQ+IaIORCRNANhgbOMfh o+80FtuWgBLKODAA== 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 4D0BE13301; Wed, 13 Nov 2024 14:45:24 +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 8oJ9EoS7NGckfQAAD6G6ig (envelope-from ); Wed, 13 Nov 2024 14:45:24 +0000 Message-ID: Date: Wed, 13 Nov 2024 15:45:24 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/5] mm: move per-vma lock into vm_area_struct Content-Language: en-US To: Lorenzo Stoakes , Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, liam.howlett@oracle.com, mhocko@suse.com, hannes@cmpxchg.org, mjguzik@gmail.com, oliver.sang@intel.com, mgorman@techsingularity.net, david@redhat.com, peterx@redhat.com, oleg@redhat.com, dave@stgolabs.net, paulmck@kernel.org, brauner@kernel.org, dhowells@redhat.com, hdanton@sina.com, hughd@google.com, minchan@google.com, jannh@google.com, shakeel.butt@linux.dev, souravpanda@google.com, pasha.tatashin@soleen.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@android.com References: <20241112194635.444146-1-surenb@google.com> <20241112194635.444146-3-surenb@google.com> <637370b8-3e3e-4457-81d6-5913a3ff1d4e@lucifer.local> 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: <637370b8-3e3e-4457-81d6-5913a3ff1d4e@lucifer.local> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: z5m3cqxmiaq6y9uoyoxu6yskgezkeigi X-Rspamd-Queue-Id: B09B440026 X-Rspamd-Server: rspam08 X-Rspam-User: X-HE-Tag: 1731509065-561479 X-HE-Meta: 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 MT1yqmTY WSyf5piBZPYlTqnuIC5nJ8ljdR80O3zR/hKwrv8RjOfNn+X9GHtIre4oPaH5haGCe0oDpOpeA/1VeByNagRvI0gBhJKJCLL9F7QxSMFYLHlyUn8cBt/zJiefaDZVtCUVkzzVhMOG7yjYjUqxrsKFlrAvnluu78H43Xp7DKfKfFQoknlg6W5WTe1xdvXC2dxI+AaPffAn2P6s96y5ZujTOJlFC6qreFzgKRDRKXbW6/FT04woPHmTs5uBJAv0iga3OVzV+7Xz8XM8gPbjmdblaKQddf8N2xTm14uGtDMEBINgi4lA/ou9IsHFGkZDOfB4FfL8xXcuskqrXoP64qAUVs8KDQNB2jj5AtmF16jCW/DK8covahcY6Bhx+72fC6HKXJ8kzsbHwfoym29ccXQvL1Y4Cow== 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 11/13/24 15:28, Lorenzo Stoakes wrote: > On Tue, Nov 12, 2024 at 11:46:32AM -0800, Suren Baghdasaryan wrote: >> Back when per-vma locks were introduces, vm_lock was moved out of >> vm_area_struct in [1] because of the performance regression caused by >> false cacheline sharing. Recent investigation [2] revealed that the >> regressions is limited to a rather old Broadwell microarchitecture and >> even there it can be mitigated by disabling adjacent cacheline >> prefetching, see [3]. > > I don't see a motivating reason as to why we want to do this? We increase > memory usage here which is not good, but later lock optimisation mitigates I'd say we don't normally split logically single structures into multiple structures just because they might pack better in multiple slabs vs single slab. Because that means more complicated management, extra pointer dereferences etc. And if that split away part is a lock, it even complicates things further. So the only motivation for doing that split was that it appeared to perform better, but that was found to be misleading. But sure it can be described better, and include the new SLAB_TYPESAFE_BY_RCU conversion part as the motivation - that would be likely impossible to do with a split away lock. > it, but why wouldn't we just do the lock optimisations and use less memory > overall? If the lock is made much smaller then the packing benefit by split might disappear, as is the case here. >> This patchset moves vm_lock back into vm_area_struct, aligning it at the >> cacheline boundary and changing the cache to be cache-aligned as well. >> This causes VMA memory consumption to grow from 160 (vm_area_struct) + 40 >> (vm_lock) bytes to 256 bytes: >> >> slabinfo before: >> ... : ... >> vma_lock ... 40 102 1 : ... >> vm_area_struct ... 160 51 2 : ... > > Pedantry, but it might be worth mentioning how much this can vary by config. > > For instance, on my machine: > > vm_area_struct 125238 138820 184 44 > >> >> slabinfo after moving vm_lock: >> ... : ... >> vm_area_struct ... 256 32 2 : ... >> >> Aggregate VMA memory consumption per 1000 VMAs grows from 50 to 64 pages, >> which is 5.5MB per 100000 VMAs. This memory consumption growth can be >> addressed later by optimizing the vm_lock. > > Yes grabbing this back is of critical importance I'd say! :) I doubt it's that critical. We'll have to weight that against introducing another non-standard locking primitive. > Functionally it looks ok to me but would like to see a stronger > justification in the commit msg! :) > >> >> [1] https://lore.kernel.org/all/20230227173632.3292573-34-surenb@google.com/ >> [2] https://lore.kernel.org/all/ZsQyI%2F087V34JoIt@xsang-OptiPlex-9020/ >> [3] https://lore.kernel.org/all/CAJuCfpEisU8Lfe96AYJDZ+OM4NoPmnw9bP53cT_kbfP_pR+-2g@mail.gmail.com/ >> >> Signed-off-by: Suren Baghdasaryan >> --- >> include/linux/mm.h | 28 +++++++++++++---------- >> include/linux/mm_types.h | 6 +++-- >> kernel/fork.c | 49 ++++------------------------------------ >> 3 files changed, 25 insertions(+), 58 deletions(-) >>