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Thu, 22 Jan 2026 19:32:20 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.88.59]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 2D8091958DC1; Thu, 22 Jan 2026 19:32:11 +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: npache@redhat.com, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, jannh@google.com, pfalcato@suse.de, jackmanb@google.com, hannes@cmpxchg.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.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, zokeefe@google.com, rientjes@google.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com Subject: [PATCH mm-unstable v14 14/16] khugepaged: avoid unnecessary mTHP collapse attempts Date: Thu, 22 Jan 2026 12:28:39 -0700 Message-ID: <20260122192841.128719-15-npache@redhat.com> In-Reply-To: <20260122192841.128719-1-npache@redhat.com> References: <20260122192841.128719-1-npache@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: TsYaH6nbZkbimSCCi9hUz90Pnnvncc-ZLwi2PFdj070_1769110340 X-Mimecast-Originator: redhat.com Content-Transfer-Encoding: 8bit content-type: text/plain; charset="US-ASCII"; x-default=true X-Stat-Signature: zpabzwpudjremgqbubj5t855pxwy3qki X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 7F88940003 X-HE-Tag: 1769110352-60631 X-HE-Meta: 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 VMT/etny Ltd9cMeBwFfv1j505s2Ycx5K+7880KLoa2RAvVimESoT2CeCAB8Jsgapg39JuMoIR36d2si5xj/WhCD7sz85+2/8jAI9Mmt5RSnf8kryM9J3mafVo9iRDUcDYuHUqIaRuwfsdZuL+E8m8MOltsynhwhyLt1IZXa5NyXvRRx26rCj6GJyIa3P+5F6BQRJEqXnURoiO7XcfkavRvFpKISwDykuP66zPzAsZ7vp+A+4ut9Y4T16aMNXQ1Y5ETmyMfUWKmVGEwrHoJbQr7fBgJek08i8rgr31PXPS0At1Uyl1Fn8H3JfKuoZhM96DuKOGaFFZEi0WYb8DPIj4/ztQFRVsVlc8Zy9hg7FScZxQ2Rk/rRuehsvJbj73updQGkW1B4+kxZQSGCO058yLayelC1SXriJ+kQNSz2nJk5/M 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: There are cases where, if an attempted collapse fails, all subsequent orders are guaranteed to also fail. Avoid these collapse attempts by bailing out early. Signed-off-by: Nico Pache --- mm/khugepaged.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 5947faaba85f..344f7cec55b4 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1499,9 +1499,42 @@ static int mthp_collapse(struct mm_struct *mm, unsigned long address, ret = collapse_huge_page(mm, collapse_address, referenced, unmapped, cc, mmap_locked, order); - if (ret == SCAN_SUCCEED) { + + switch (ret) { + /* Cases were we continue to next collapse candidate */ + case SCAN_SUCCEED: collapsed += nr_pte_entries; + fallthrough; + case SCAN_PTE_MAPPED_HUGEPAGE: continue; + /* Cases were lower orders might still succeed */ + case SCAN_LACK_REFERENCED_PAGE: + case SCAN_EXCEED_NONE_PTE: + case SCAN_EXCEED_SWAP_PTE: + case SCAN_EXCEED_SHARED_PTE: + case SCAN_PAGE_LOCK: + case SCAN_PAGE_COUNT: + case SCAN_PAGE_LRU: + case SCAN_PAGE_NULL: + case SCAN_DEL_PAGE_LRU: + case SCAN_PTE_NON_PRESENT: + case SCAN_PTE_UFFD_WP: + case SCAN_ALLOC_HUGE_PAGE_FAIL: + goto next_order; + /* Cases were no further collapse is possible */ + case SCAN_CGROUP_CHARGE_FAIL: + case SCAN_COPY_MC: + case SCAN_ADDRESS_RANGE: + case SCAN_NO_PTE_TABLE: + case SCAN_ANY_PROCESS: + case SCAN_VMA_NULL: + case SCAN_VMA_CHECK: + case SCAN_SCAN_ABORT: + case SCAN_PAGE_ANON: + case SCAN_PMD_MAPPED: + case SCAN_FAIL: + default: + return collapsed; } } -- 2.52.0