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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id F2D11D65C43 for ; Wed, 17 Dec 2025 12:55:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3D6206B008A; Wed, 17 Dec 2025 07:55:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 3A4116B008C; Wed, 17 Dec 2025 07:55:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2ACFA6B0092; Wed, 17 Dec 2025 07:55:51 -0500 (EST) 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 183196B008A for ; Wed, 17 Dec 2025 07:55:51 -0500 (EST) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 977F1140AA5 for ; Wed, 17 Dec 2025 12:55:50 +0000 (UTC) X-FDA: 84228960060.23.7736374 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.223.131]) by imf11.hostedemail.com (Postfix) with ESMTP id 268F840009 for ; Wed, 17 Dec 2025 12:55:47 +0000 (UTC) Authentication-Results: imf11.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=uxwtsLIO; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=IiEo+OmL; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=uxwtsLIO; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=IiEo+OmL; spf=pass (imf11.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 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=1765976148; 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=4arLgLyyhNXwodcIP94lI9F5JTrR8TRXcuQJUxnRcKQ=; b=1URffsRUgBflFvBDkhiOVyCpT0/6/N0asAKqViTlIPL3mGLyXjjX6khn12pxjq9R/2Vhnz 175leZVb8eQf16T9COMqdrKnj9857+ZHKIqJJlarSHmIX/JV3PyNjjAA35OFO+rID3hlAU RhoNyjLo3i2pFTqOBesq70SWEozr7d8= ARC-Authentication-Results: i=1; imf11.hostedemail.com; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=uxwtsLIO; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=IiEo+OmL; dkim=pass header.d=suse.cz header.s=susede2_rsa header.b=uxwtsLIO; dkim=pass header.d=suse.cz header.s=susede2_ed25519 header.b=IiEo+OmL; spf=pass (imf11.hostedemail.com: domain of vbabka@suse.cz designates 195.135.223.131 as permitted sender) smtp.mailfrom=vbabka@suse.cz; dmarc=none ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1765976148; a=rsa-sha256; cv=none; b=xRljekD6pmXiqnWMc9I/6aOkpm0L1qMslsiKNUR12AP9llBkbhnmDwzcGs2S1t+naWjlIA d+e46aWEKY8ebfe0xBMHK0woM/rw5i7vUt9uLbLmyRO7MfgzbulTpEBxwLgU5V7nNwFmj9 13T+yTQEEBJg96jUhrhi+jpd1DTysrA= 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 6E18C5BCF8; Wed, 17 Dec 2025 12:55:46 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1765976146; 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=4arLgLyyhNXwodcIP94lI9F5JTrR8TRXcuQJUxnRcKQ=; b=uxwtsLIOfz7+HXrJxVeuuOq01z9d9e/dsNknxRx7k1n+jQ3Jg+IWlO8jH2CzOdsR2ozGmY g+FLLB6dboWj3JWpHl0dT0tfw1OY27VJStXMOWgAidgGm4bNmU0Pw7u3o51aofYi4+SVQR Wjb73IgW1BGUA5TPK/f77HZER1s+1ag= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1765976146; 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=4arLgLyyhNXwodcIP94lI9F5JTrR8TRXcuQJUxnRcKQ=; b=IiEo+OmLWr7PYKnjVaYOSZ2QhiJ3u7FuFf/6svO1osZ/uxMPcdBn+pNgjBahWiiYhDGnM/ ZWob8gsw+zqG00Ag== DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_rsa; t=1765976146; 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=4arLgLyyhNXwodcIP94lI9F5JTrR8TRXcuQJUxnRcKQ=; b=uxwtsLIOfz7+HXrJxVeuuOq01z9d9e/dsNknxRx7k1n+jQ3Jg+IWlO8jH2CzOdsR2ozGmY g+FLLB6dboWj3JWpHl0dT0tfw1OY27VJStXMOWgAidgGm4bNmU0Pw7u3o51aofYi4+SVQR Wjb73IgW1BGUA5TPK/f77HZER1s+1ag= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.cz; s=susede2_ed25519; t=1765976146; 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=4arLgLyyhNXwodcIP94lI9F5JTrR8TRXcuQJUxnRcKQ=; b=IiEo+OmLWr7PYKnjVaYOSZ2QhiJ3u7FuFf/6svO1osZ/uxMPcdBn+pNgjBahWiiYhDGnM/ ZWob8gsw+zqG00Ag== 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 3D7D73EA63; Wed, 17 Dec 2025 12:55:46 +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 qROsDlKoQmklMwAAD6G6ig (envelope-from ); Wed, 17 Dec 2025 12:55:46 +0000 Message-ID: <01d780a3-16ef-4f87-b57d-00d50afa4bed@suse.cz> Date: Wed, 17 Dec 2025 13:55:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 2/2] mm/vmscan: don't demote if there is not enough free memory in the lower memory tier Content-Language: en-US To: Akinobu Mita Cc: linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, hannes@cmpxchg.org, david@kernel.org, mhocko@kernel.org, zhengqi.arch@bytedance.com, shakeel.butt@linux.dev, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, rppt@kernel.org, surenb@google.com References: <20251208094028.214949-1-akinobu.mita@gmail.com> <20251208094028.214949-3-akinobu.mita@gmail.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+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20251208094028.214949-3-akinobu.mita@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: 5c3pnh7g4zx5fo618xyca6tkzbuugtb6 X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 268F840009 X-HE-Tag: 1765976147-987495 X-HE-Meta: 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 fuNEKx+o AmQhHMkcTZiQEQEtCGAoba4kA9GPYdJMFsdAbeN6hbeonRbo3CW6SSUoNco8izRrdpYePckNlMQ5sW+5nbE9rPsl0xf34lewCYpOsF15J4ZK4lESKgrcxSRMhkLSvoXQ9d9t0FvwGeL7tGefpgcYQ9jKaYKkf5Ev4wx04b0FM0KrgyFAb9sZnQRwRK61HersKLUeihLAkT7XThWwmTXZuVL48NS1T7ANhidFIaG2Ga2o0JiwbkCY+cajvDRmBdoh4kldq8/r9E2UvlF+bZ4hSK4Qqzt7xItIvpqjPbfOTjKwevvVzFeonMGNyTM20ORB9VVZoHJmaZDlthxboiquPwguE4YTVH0WBmyevRzb84FkKExARXh17ailwmrkbp0/oLyDP59Z7QVFRi6hMV2XNtH7tvYT9VNCsoD0A 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 12/8/25 10:40, Akinobu Mita wrote: > On systems with multiple memory-tiers consisting of DRAM and CXL memory, > the OOM killer is not invoked properly. > > Here's the command to reproduce: > > $ sudo swapoff -a > $ stress-ng --oomable -v --memrate 20 --memrate-bytes 10G \ > --memrate-rd-mbs 1 --memrate-wr-mbs 1 > > The memory usage is the number of workers specified with the --memrate > option multiplied by the buffer size specified with the --memrate-bytes > option, so please adjust it so that it exceeds the total size of the > installed DRAM and CXL memory. > > If swap is disabled, you can usually expect the OOM killer to terminate > the stress-ng process when memory usage approaches the installed memory > size. > > However, if multiple memory-tiers exist (multiple > /sys/devices/virtual/memory_tiering/memory_tier directories exist), > and /sys/kernel/mm/numa/demotion_enabled is true and > /sys/kernel/mm/lru_gen/min_ttl_ms is 0, the OOM killer will not be invoked Does this mean only mglru has the problem, or !mglru too? Also is min_ttl_ms = 0 a sensible setting? What happens without it? If !mglru doesn't have this problem, how does the fix affect it? > and the system will become inoperable. > > This issue can be reproduced using NUMA emulation even on systems with > only DRAM. You can create two-fake memory-tiers by booting a single-node > system with "numa=fake=2 numa_emulation.adistance=576,704" kernel > parameters. > > The reason for this issue is that if the target node for allocation has > an underlying memory tier, it is always assumed that it can be reclaimed > via demotion. > > So this change avoids this issue by not attempting to demote if the > demoting node has less free memory than the minimum watermark. > > Signed-off-by: Akinobu Mita > --- > mm/vmscan.c | 15 ++++++++++++++- > 1 file changed, 14 insertions(+), 1 deletion(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index fddd168a9737..f4748f258294 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -356,7 +356,20 @@ static bool can_demote(int nid, struct scan_control *sc, > return false; > > /* If demotion node isn't in the cgroup's mems_allowed, fall back */ > - return mem_cgroup_node_allowed(memcg, demotion_nid); > + if (mem_cgroup_node_allowed(memcg, demotion_nid)) { > + int z; > + struct zone *zone; > + struct pglist_data *pgdat = NODE_DATA(demotion_nid); > + unsigned int highest_zoneidx = sc ? sc->reclaim_idx : MAX_NR_ZONES - 1; > + int order = sc ? sc->order : 0; > + > + for_each_managed_zone_pgdat(zone, pgdat, z, highest_zoneidx) { > + if (zone_watermark_ok(zone, order, min_wmark_pages(zone), > + highest_zoneidx, 0)) > + return true; > + } > + } > + return false; > } > > static inline bool can_reclaim_anon_pages(struct mem_cgroup *memcg,