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Thu, 17 Apr 2025 00:07:10 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.88.34]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 809E1180045B; Thu, 17 Apr 2025 00:07:02 +0000 (UTC) From: Nico Pache To: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org Subject: [PATCH v4 08/12] khugepaged: skip collapsing mTHP to smaller orders Date: Wed, 16 Apr 2025 18:02:34 -0600 Message-ID: <20250417000238.74567-9-npache@redhat.com> In-Reply-To: <20250417000238.74567-1-npache@redhat.com> References: <20250417000238.74567-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 719E8C0006 X-Stat-Signature: ab3ya8s8n7suqihiad8jy18kba3rbrhi X-Rspam-User: X-HE-Tag: 1744848438-182349 X-HE-Meta: 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 4AQytmcu tCrtgvFKw4ROJ3O1fL45Vmv/9oSFNJGgAnayoHftf3GpD+URJfIOXRAuQvkF9AfSZgnIanbffxpcGKuByTXr21kwn42hJYJi0KyeofAMKvDm/ktjLCa95O+gOVZYvIslkFg68cu8aTSnyO88s+0TAnlxROY3Slc8i6iQv24sLaReSY2A5KkbUo3ANPd8OHn5mOp40I+7T1xXtF/M6XqB0pvbm+Q412QR2T19rv02NSwV+99z3edA8O6rardoDj4g2OAtin93+hruTzylC2Y1XvKGNHmTCPvwwgDO97Fukpk2Mo2j5fPJYoEiWP0uGdc1796XDNn6xM+aJejfudJ6Rco2Hr+iI+s6CZI2Wsk24N4rJxPBV31ge/ilqau1wkSZYbzWdK22xVQ8OhPgKR3sOQcOulLmJbhN1TpajQMcHa2bFtPT8lirAxoKKJedrGv1BlUPjZn3/+q4XR42VonhWS4pH6zxW/fattAgkiBSmhUs79T4= 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: khugepaged may try to collapse a mTHP to a smaller mTHP, resulting in some pages being unmapped. Skip these cases until we have a way to check if its ok to collapse to a smaller mTHP size (like in the case of a partially mapped folio). This patch is inspired by Dev Jain's work on khugepaged mTHP support [1]. [1] https://lore.kernel.org/lkml/20241216165105.56185-11-dev.jain@arm.com/ Co-developed-by: Dev Jain Signed-off-by: Dev Jain Signed-off-by: Nico Pache --- mm/khugepaged.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index ece39fd71fe6..383aff12cd43 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -625,7 +625,12 @@ static int __collapse_huge_page_isolate(struct vm_area_struct *vma, folio = page_folio(page); VM_BUG_ON_FOLIO(!folio_test_anon(folio), folio); - /* See hpage_collapse_scan_pmd(). */ + if (order != HPAGE_PMD_ORDER && folio_order(folio) >= order) { + result = SCAN_PTE_MAPPED_HUGEPAGE; + goto out; + } + + /* See khugepaged_scan_pmd(). */ if (folio_maybe_mapped_shared(folio)) { ++shared; if (order != HPAGE_PMD_ORDER || (cc->is_khugepaged &&