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b=twcijVYD2M7rlK1ysyxLBn6orH1nphJ6IxRQuXyuq7kG88S6D69CaVbMlmCZ+8PPc7qP9VLT5jDnYIyWLSwdw+oCRJDJGAOxlkcDYAMHrZ8cj1T+SRmBdIwMwy31WDX/dl2mORaAO/OU110iBPrW2CQ4+bRoFsgafAii85PMlQU= Received: from 30.74.146.225(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WXyG8sZ_1745480926 cluster:ay36) by smtp.aliyun-inc.com; Thu, 24 Apr 2025 15:48:47 +0800 Message-ID: Date: Thu, 24 Apr 2025 15:48:45 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 08/12] khugepaged: skip collapsing mTHP to smaller orders To: Nico Pache , 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, 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 References: <20250417000238.74567-1-npache@redhat.com> <20250417000238.74567-9-npache@redhat.com> From: Baolin Wang In-Reply-To: <20250417000238.74567-9-npache@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: 0F5B3C0005 X-Stat-Signature: gga5hn6s1jf1fhgfey3n51feqni1b9be X-Rspam-User: X-HE-Tag: 1745480931-248120 X-HE-Meta: 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 VhnTT7vq +gTSlWgCOOa7DKjzmMW1dAID4z+GDI65Ar+rK2nrK/Sy8Wcm5t9kVi6uX/DuZOhtmqwJHB5v3JqJbvAZWLAwqVhdZuzEkVFBlYw3tLVF/X9lkL//0iRFmSem4pJkq8XbeXBib4q5IIw/ZmL847Ozk8nwP7jH4LAJx2eb72qEJJrc7wBO+TojEgqVk53VuCTa70vGEO+pobXgjUOLkP1ckGaBdNQinpenZmhWvFMFj9z8zTg/OP24ex3FM9oi7OJTdrTdIpXx1Ow0G5FQ9RnDgHlrvK9loPVbJPaLsSsjrzS2bsOfkbNNjh/5AakZb+agQO3owbEhX6tqX2l9VyGBd0PGdBz2SBz4wDudPboWpFMc2S+lq7XFmJ/FG+2JlHZzguH3KWf78LEot55mfjo58KxobQ9o483Eg91CHl0UtFitWL5E= 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 2025/4/17 08:02, Nico Pache wrote: > 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; > + } Should we also add this check in hpage_collapse_scan_pmd() to abort the scan early?