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 D9FA7C4345F for ; Fri, 12 Apr 2024 07:41:30 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 429C76B0098; Fri, 12 Apr 2024 03:41:30 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3DAA56B0099; Fri, 12 Apr 2024 03:41:30 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 252996B009A; Fri, 12 Apr 2024 03:41:30 -0400 (EDT) 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 06D7D6B0098 for ; Fri, 12 Apr 2024 03:41:30 -0400 (EDT) Received: from smtpin26.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id C7DA840DA2 for ; Fri, 12 Apr 2024 07:41:29 +0000 (UTC) X-FDA: 82000084698.26.A44A52E Received: from smtp-out1.suse.de (smtp-out1.suse.de [195.135.223.130]) by imf08.hostedemail.com (Postfix) with ESMTP id 4959016000A for ; Fri, 12 Apr 2024 07:41:26 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="VyEif3/6"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=lqdYEwNv; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="VyEif3/6"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=lqdYEwNv; spf=pass (imf08.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1712907686; 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=bpSFbvpuwKnjTjJW94zNuOLDHd0xHPzUBCV4nRLI79c=; b=kAbZ/xW2UfcV4p0P4NGFioqaNCbiuv90lKxukoGDUZmjmv0jeTH885oS4rkq6mllTnMl8D 6qfr2tM0oDuXhPuEIaX/ACWQHJLc58XoC1WN5pU/EjNuUWSpYPL+m4sp4h9ojpUe8UH5yp vYDX4Au1MLskhNHxm5tghnH0aKjRgPs= ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="VyEif3/6"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=lqdYEwNv; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b="VyEif3/6"; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=lqdYEwNv; spf=pass (imf08.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.130 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1712907686; a=rsa-sha256; cv=none; b=wzz83elXLLjOhBamJ7s6ntjPgXEQSrAGRngtwcb4neNX7BKMxYoEN+C1w+PCH/FDSMUHgz xetvbkZDx5pCded2oCbQ48MQlK2WsHLGktf4vokULE+3ZWrRicglHqLTTpckIVlUa9eY0K exKRlywj6x1JUZ9QR4/WIsjSdaxUUmk= Received: from imap1.dmz-prg2.suse.org (imap1.dmz-prg2.suse.org [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 5D46E37FDE; Fri, 12 Apr 2024 07:41:24 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1712907684; 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=bpSFbvpuwKnjTjJW94zNuOLDHd0xHPzUBCV4nRLI79c=; b=VyEif3/6Z89z11ZwgChc/btbqf4QnyeeunUA4I0JWys+Jl1l0VclIC7eulkAZ5OodwjpbK 9KCLTNB7UymteSbVvLAZjv/I8M0xqeNaLJNJm7o8opCLzKDhY0wCLnIIL6VZqMSpcjpGEq zmF/9n6eY8foszg4T77O0orY5pg8lVc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1712907684; 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=bpSFbvpuwKnjTjJW94zNuOLDHd0xHPzUBCV4nRLI79c=; b=lqdYEwNvYSXrknr3BSOjxkEem4es0xUNCDaYCd2B7ECUOJiHS41jIHVHJmmWXAd9gto3h9 qbZjJ1zcb3aatXAQ== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1712907684; 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=bpSFbvpuwKnjTjJW94zNuOLDHd0xHPzUBCV4nRLI79c=; b=VyEif3/6Z89z11ZwgChc/btbqf4QnyeeunUA4I0JWys+Jl1l0VclIC7eulkAZ5OodwjpbK 9KCLTNB7UymteSbVvLAZjv/I8M0xqeNaLJNJm7o8opCLzKDhY0wCLnIIL6VZqMSpcjpGEq zmF/9n6eY8foszg4T77O0orY5pg8lVc= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1712907684; 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=bpSFbvpuwKnjTjJW94zNuOLDHd0xHPzUBCV4nRLI79c=; b=lqdYEwNvYSXrknr3BSOjxkEem4es0xUNCDaYCd2B7ECUOJiHS41jIHVHJmmWXAd9gto3h9 qbZjJ1zcb3aatXAQ== 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 4A83013942; Fri, 12 Apr 2024 07:41:24 +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 u67ZEaTlGGYKbgAAD6G6ig (envelope-from ); Fri, 12 Apr 2024 07:41:24 +0000 Message-ID: Date: Fri, 12 Apr 2024 09:41:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] slub: limit number of slabs to scan in count_partial() To: Jianfeng Wang , linux-mm@kvack.org, linux-kernel@vger.kernel.org Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com, iamjoonsoo.kim@lge.com, akpm@linux-foundation.org, junxiao.bi@oracle.com References: <20240411164023.99368-1-jianfeng.w.wang@oracle.com> 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: <20240411164023.99368-1-jianfeng.w.wang@oracle.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4959016000A X-Rspam-User: X-Stat-Signature: n1dsg9azpehoc5yt1qscy9pmj7kaf3zi X-Rspamd-Server: rspam01 X-HE-Tag: 1712907686-421557 X-HE-Meta: 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 Sro5ZENi 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 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 4/11/24 6:40 PM, Jianfeng Wang wrote: > When reading "/proc/slabinfo", the kernel needs to report the number > of free objects for each kmem_cache. The current implementation relies > on count_partial() that counts the number of free objects by scanning > each kmem_cache_node's list of partial slabs and summing free objects > from every partial slab in the list. This process must hold per > kmem_cache_node spinlock and disable IRQ and may take a long time. > Consequently, it can block slab allocation requests on other CPU cores > and cause timeouts for network devices etc., when the partial slab list > is long. In production, even NMI watchdog can be triggered due to this > matter: e.g., for "buffer_head", the number of partial slabs was > observed to be ~1M in one kmem_cache_node. This problem was also Wonder what led to such a situation, whether it could have been the NUMA related problem this patch is fixing: https://lore.kernel.org/all/20240330082335.29710-1-chenjun102@huawei.com/ But guess we don't do that with buffer heads, and it's just possible that a surge of allocations led to many slabs being allocated, and then the a slower trickle freeing didn't happen in a matching order, leading to many slabs becoming partially free... > confirmed by several others [1-3] in the past. > > Iterating a partial list to get the exact count of objects can cause > soft lockups for a long list with or without the lock (e.g., if > preemption is disabled), and is not very useful too: the object > count can change right after the lock is released. The approach of > maintaining free-object counters requires atomic operations on the > fast path [3]. > > So, the fix is to limit the number of slabs to scan in > count_partial(), and output an approximated result if the list is too > long. Default to 10000 which should be enough for most sane cases. > > [1] https://lore.kernel.org/linux-mm/ > alpine.DEB.2.21.2003031602460.1537@www.lameter.com/T/ > [2] https://lore.kernel.org/lkml/ > alpine.DEB.2.22.394.2008071258020.55871@www.lameter.com/T/ > [3] https://lore.kernel.org/lkml/ > 1e01092b-140d-2bab-aeba-321a74a194ee@linux.com/T/ > > Signed-off-by: Jianfeng Wang > --- > mm/slub.c | 11 ++++++++++- > 1 file changed, 10 insertions(+), 1 deletion(-) > > diff --git a/mm/slub.c b/mm/slub.c > index 1bb2a93cf7b6..5ed998ec7d6d 100644 > --- a/mm/slub.c > +++ b/mm/slub.c > @@ -3213,16 +3213,25 @@ static inline bool free_debug_processing(struct kmem_cache *s, > #endif /* CONFIG_SLUB_DEBUG */ > > #if defined(CONFIG_SLUB_DEBUG) || defined(SLAB_SUPPORTS_SYSFS) > +#define MAX_PARTIAL_TO_SCAN 10000 > + > static unsigned long count_partial(struct kmem_cache_node *n, > int (*get_count)(struct slab *)) > { > unsigned long flags; > unsigned long x = 0; > + unsigned long scanned = 0; > struct slab *slab; > > spin_lock_irqsave(&n->list_lock, flags); > - list_for_each_entry(slab, &n->partial, slab_list) > + list_for_each_entry(slab, &n->partial, slab_list) { > x += get_count(slab); > + if (++scanned > MAX_PARTIAL_TO_SCAN) { > + /* Approximate total count of objects */ > + x = mult_frac(x, n->nr_partial, scanned); > + break; > + } > + } > spin_unlock_irqrestore(&n->list_lock, flags); > return x; > }