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 8866CC88E7D for ; Tue, 15 Sep 2026 16:17:41 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 8F0F86B008C; Tue, 15 Sep 2026 12:17:40 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8A0BE6B0092; Tue, 15 Sep 2026 12:17:40 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7B7F46B0093; Tue, 15 Sep 2026 12:17:40 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 5A5FD6B008C for ; Tue, 15 Sep 2026 12:17:40 -0400 (EDT) Received: from smtpin30.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 927CDA04AF for ; Tue, 15 Sep 2026 16:17:39 +0000 (UTC) X-FDA: 85216502238.30.75D9150 Received: from mail-qk1-f174.google.com (mail-qk1-f174.google.com [209.85.222.174]) by imf29.hostedemail.com (Postfix) with ESMTP id 7DD0C120008 for ; Tue, 15 Sep 2026 16:17:37 +0000 (UTC) Authentication-Results: imf29.hostedemail.com; dkim=pass header.d=cmpxchg.org header.s=google header.b=J6HuFXQZ; spf=pass (imf29.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.222.174 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (policy=none) header.from=cmpxchg.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1789489057; b=SCzb2NbOUQ4a4RYdE+AmSKurKRH9ObGhYjRedFuy5Q8BmF+TGFWPfmP2CdRpdqHrfp28Ra NWGLWA1pzNYv5pk3nmUgAvyJp0XiLjRwxqMAzeKNjEnkoXpL6JJ6dzdeiFeavI8bJB/5Ro dtwpmPDQQzuOiBnOt2Q482rU/YO0/aI= ARC-Authentication-Results: i=1; imf29.hostedemail.com; dkim=pass header.d=cmpxchg.org header.s=google header.b=J6HuFXQZ; spf=pass (imf29.hostedemail.com: domain of hannes@cmpxchg.org designates 209.85.222.174 as permitted sender) smtp.mailfrom=hannes@cmpxchg.org; dmarc=pass (policy=none) header.from=cmpxchg.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1789489057; 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: in-reply-to:in-reply-to:references:references:dkim-signature; bh=dXoaSOzLcSniPHeJqnrgZd+b23tx7/MvhGFOoQXutdY=; b=bk07BLLliz9tawrqf9tNeZnS6QKRUB+qDigAY3+irAeqRzBCohRnKgkn6Y1tpS+wD3NXvF ybZhEEFbrSiu3QRV/1pOp23fYFSCV0ZA71kg0OS0tgaxD/qBQPxxIKmqoIlg3GhrSIEwbY lXG6zPMsQsi9sqpYABa6KCtTFnLdZjo= Received: by mail-qk1-f174.google.com with SMTP id af79cd13be357-93a0fb2f9efso78060785a.1 for ; Tue, 15 Sep 2026 09:17:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cmpxchg.org; s=google; t=1789489056; x=1790093856; darn=kvack.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=dXoaSOzLcSniPHeJqnrgZd+b23tx7/MvhGFOoQXutdY=; b=J6HuFXQZYUBEHu0xrbK680ivDkp3AU+Vfi9aqYK6h56lKqpk7ThzliVq9zenGqF0lN CSbGA6y63QZWFEtb7SEf7Pj5RGVO9FQbElDUj08wDF9qVco42ljQBxoZ1Q78geZs4ttw B+MnEbDFTwXR2FJNRPlkWGnlOPm3KVtUfeQmI0GoUumvu+G1Z5NRipeK15W1d7uCEYbG a5uO5rYDM+mokTnNMdtCqWHQAhQPfAEFPHswKTWqm+jdM8dSPg09NFnFdGebY73D3PXB Ns2yGl6pNlASxoSa196ufZRCMtgzUman8SZn6QNG2ML6bp5Ch29deYMsMYUAzf8yCihY mGVQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789489056; x=1790093856; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=dXoaSOzLcSniPHeJqnrgZd+b23tx7/MvhGFOoQXutdY=; b=v+XxncQvROTPxkvgCLE6vu8+WVCNlGepbNw7vYZbwr5hKLtaIMswcOyyrjHTze41vl q4CG8+/ul4CK7dfAmxt8voKInOHjKkvGqReVBn56SODsSsHcHqSIK0nUvhM3oqaX0jHY WWMaH9JSJqkumnTEuKgBmEnSbTsyJaxE91G9tU0osqahF7hmNZYPeZiIha2bHYGPudYN Bv0LwCOorSNsJBVWxfjbhS4fopvVl6luF9M0Hcx2Z9DXluRUZC+VcU386YrdvxJZYnzy lqP3lwM0/RUjkiO2I9KQUX0C3LUnrDwQktrpHKtC5ZPegHgchk9iga2RbXfUFNjGem/J 1+TQ== X-Forwarded-Encrypted: i=1; AKwUvBzGdgnZbtJxo4UVIXfQEfpPpTIHOETGFykIn8yoK7HeEW6NFYkCEaMH4OJAeUQCntHuXhZb68hUtA==@kvack.org X-Gm-Message-State: AFuF++nrdq3t2Xanidh3HWXrrbtJBfnf7eGzAcGQMSFmT6HCmxVRzcPd 89FK51iuBFP+ToCYCDcSEbNIpsxNNepZo+BAHJ5i65t9PYxd4K+q++Ugm59lCB93CKk= X-Gm-Gg: AYBFou2C+DjeCE9++tF5kBftgMcVVSsyiPyrqxA/oGDRwxKYSZ6cCkoKQlUdZWa8XMB yqeTDszKs5tpmnZnCeaJUMW1WKnvb5cHq3Un35gpkmRbAdYazoLO7oVNzSmazGre/adl2gYrpvf gVCYktFcdp2dzG1LUOSTNxwOKiQIEx6dY3I3Fx4xV4qUdhIpqReJ98w0KiUCtBmVnvG9YdvZivK Ks9U+4jC7RlU5QfFoujCqdArBNIyQm7JSdRgfIzmso8x8MieL/QiHJoJT3kiTJW+24CMPLAXzst 92bFZLJjFGpkSzlJ42jioTSyG3k8ObKv6ELtPq1hQbchGTH3AKuiSUQ3OJAObkb761cVannviwx brmk2a8prRp0pOyGKgQd3k4igDdsck/KFIU2dOAH+a4Y7eGn54AhkxLDbRzfFfNCixNyfPyiN0b MS7N6schOpemx5iemmxjYyMbUpfrX/CUFa5bfSAFGd1db3UgRXf0OUzU/Jv1dq0xzr+Q/v/A== X-Received: by 2002:a05:620a:2607:b0:939:b7f4:c7dd with SMTP id af79cd13be357-93a3477ff9cmr603922085a.47.1789489055702; Tue, 15 Sep 2026 09:17:35 -0700 (PDT) Received: from localhost ([2603:7001:f100:500:365a:60ff:fe62:ff29]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-9123bddd5e1sm2362876d6.3.2026.09.15.09.17.34 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 15 Sep 2026 09:17:35 -0700 (PDT) Date: Tue, 15 Sep 2026 12:17:34 -0400 From: Johannes Weiner To: Salvatore Dipietro Cc: akpm@linux-foundation.org, abuehaze@amazon.com, alisaidi@amazon.com, blakgeof@amazon.com, brauner@kernel.org, brendan.jackman@linux.dev, david@redhat.com, dgc@kernel.org, dipietro.salvatore@gmail.com, djwong@kernel.org, hch@infradead.org, hch@lst.de, jackmanb@google.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-xfs@vger.kernel.org, mhocko@suse.com, ritesh.list@gmail.com, rvvandan@amazon.com, stable@vger.kernel.org, surenb@google.com, vbabka@kernel.org, vbabka@suse.cz, willy@infradead.org, ziy@nvidia.com Subject: Re: [PATCH v5] mm/page_alloc: avoid direct compaction for costly __GFP_NORETRY allocations Message-ID: References: <20260911093209.d9181d5950778897935f6bcb@linux-foundation.org> <20260915160042.1265958-1-dipiets@amazon.it> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260915160042.1265958-1-dipiets@amazon.it> X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 7DD0C120008 X-Rspam-User: X-Stat-Signature: cky51pamiog5hr4mjt69rjquixrkyiur X-HE-Tag: 1789489057-840024 X-HE-Meta: U2FsdGVkX1+m/gxys732knMhja1exkCbfOtCyclUfqODkudKQs9FCIvkB59PTQCfB3CvlH/mnSvqyVALxowLElgwOPpOK48yJoe0x6/MCer7mT3thBThZesfzYdwlXlGhUOt4SvngIZ/VdGK4Xr/yoJgAGm4n18w9ZDnTR6QvhGdyFx6XIh3Te56H5IZSO4BGzYjUdPxtganiWRmUYM0UqktMHfNTTX3aw1kmX046TpP8VKk1miEFiG4WJZyxg87faBpFLCBpNkvbKsad2bomxeYE9vfm+SptbCgI68B7Zg7o3EiuKeRzMm9dPDmPRzsaZV1HmUuXDxhQjS3XCpga3eXvMxZ4VgWQ/Ig0VaEgTYTHLOtuAHdqxRXCf+qbg5g2rLVaN1LAwVd39/VXwa34ieaHZHDVYK+Pn2+qjv0nqGh8ZEO7I4/7lvXQ2RMspJt1PHt/chqU/qzD8QcGslJKX+lKv7uHdhbqji9fHGalk1EWi1Pbw6FHcSTevRDkdg/1nu0qehLwrooPRUhQp7XA3cfqeXv12JOpu/VDGwfU3IpwdHezFyR5194vqVD7lQTIiSWst75FMSX5xswIH/yAnQjH9//kBscYnlO3wfF9A6dTCmGu2oyeFpktxQADxPLRAZLVtOOaUtPEefxy1TE/H32zJdVJLrNU+b1q0KnVt1ZXUjqSMUlz0FZaVGlE5mXIck+ezOakGgdd6fXXH0RJcY4nd+0jtaitND5t0RIKfiDVMMEyVfwgDbU3gIKUSsYo9MHak64VRXePPUXNJjDb4g5poxmEfm7msVy8NJpr8m4Q+wSjG26AVi8ZIMzuDsqmi0MNEDw+FGZGQvKvMRG/4ApPvb3z3RmF7bYaTq7MHVDzq+dmVPHYaM50MCdrISkCUn1mv0jxNPFT4wLE9E2fvfIIxoVGlMMEfTccJ3imYsLoIaJHnnuHiJNFH2xvW/2jhbjmn33CTyN39qcTRC hptV/ZhA 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Sep 15, 2026 at 04:00:42PM +0000, Salvatore Dipietro wrote: > > On Fri, 11 Sep 2026 09:32:00 -0700 Andrew Morton wrote: > > > does any of this look real? > > The mechanism seems real, but it only shows up with vm.defrag_mode=1, > which is off by default. > > With defrag_mode=1, a costly __GFP_NORETRY allocation that used to fail > cleanly can now succeed by fragmenting another migratetype's pageblock, > which seems like the wrong trade for a caller whose premise is a cheap > lower-order fallback. Johannes, do we want to keep it strict? Yes, avoiding the fallback is a good idea. The user already communicated they can handle failure and have fallback options. > If so, we could add a condition like below. It is equally > applicable to v4 and v5. Happy to send it separately or in v6. > > /* > * Reclaim/compaction cannot run, so defrag_mode's strategy > * of enforcing ALLOC_NOFRAGMENT cannot be fulfilled. Allow > * fallbacks rather than failing the allocation outright. > * Not for costly __GFP_NORETRY: those have a cheap lower > * order fallback, so failing beats fragmenting. > */ > if (defrag_mode && (alloc_flags & ALLOC_NOFRAGMENT) && > !(costly_order && (gfp_mask & __GFP_NORETRY)) && It would be possible to remove the costly_order gate here and just bail on __GFP_NORETRY. But no strong feelings.