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Thu, 11 Sep 2025 23:31:32 -0400 X-MC-Unique: 8MqFEGeOPS2NV-lcySUhFw-1 X-Mimecast-MFC-AGG-ID: 8MqFEGeOPS2NV-lcySUhFw_1757647887 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-02.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 6C9471956086; Fri, 12 Sep 2025 03:31:27 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.80.28]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 68CC81800451; Fri, 12 Sep 2025 03:31:18 +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: david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.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, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de Subject: [PATCH v11 13/15] khugepaged: avoid unnecessary mTHP collapse attempts Date: Thu, 11 Sep 2025 21:28:08 -0600 Message-ID: <20250912032810.197475-14-npache@redhat.com> In-Reply-To: <20250912032810.197475-1-npache@redhat.com> References: <20250912032810.197475-1-npache@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 X-Rspamd-Queue-Id: 547D680003 X-Stat-Signature: qnjozqd1w4apd1ykajsz4ewttnapbfrs X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1757647896-341555 X-HE-Meta: U2FsdGVkX1+oEcGPlpUPLlTt3PtFbBymwnu9JSVdbFRJtRkl1LFf+5sHsSzfvcT7IstKyGshaFVZy/ahFjph7Rp31peBRs7AFTmpj8AO/vFZ7c9HEXYqT/99hHXYWbQU/ueZxB2WQ9ulOG4TRzJ5AtVIT6eztoPpZ6iq4HyqFCoGx/8Ud+uh56xjBqWfBN50DWZdLWPxdLpVESvpLzFBULNAES5VTS6rpKpcQopSAA7RGWmMzdfmP8G0vu3e6e4pOfXLBKAQUXmW2k27fzeCNduBTlVgKYelCENb4885fY2D7nSZkSbqawG6DrfQwullPilayIBlyV7vrzECHJ1prN0qpwmZ4Obp/HGe+F902BQYf41Vo0E33IpCg2N54SMUf/sYdXFHJ1ypnV2Qt78Qdm18dAVE0wxHgJSmYPLU8CKz+rGkRbSFxbG8L7rL//0AlaQYuuMtrTLtQvV5pPcfL1YKffdZbXCO/M8xgt1ch+gPWdRdObY71MsKCwvYkMnbPrzAkAmYHI4e5ukrkoh+I5DDFnhK9WCuYQrefT3yLxOILzIE71uIKMSa0AfcFn2BTF1rWSE6y+s0jOfYk1w/HnZz/GPrrtlcVx89Lmsb1x1BeXmLcDa1n+1sxXAEookE17UoUdxvf/r7EPyLvShPti+yUIMEQ/Fk6D5dP00ZKNhFkTnRp3jxtow8qK4xnP+scAE1nQxv+r1b5ax6fI5wzKFbny6e8T9UJv3smdKxKE+O75/r3Xf8B+HNWEgoQ5CRfOveZZG9lG3edcgzk0AauA0AnLho+CvNmR4ZZUsDmRJS6NdJAyBHPyjlckHbhVEBuzw0HUlP27cUkz6Jdb/e4vaMU3zOAXVYAi/p5+zBRq+vBvo860ohvQ9Yrg67nmm8VP4I1op20q8AsPVIDtjV9hv6Jv1ejKv5IwaCLaofhktRbnD3lrMNdjJPlJUeVrZSHlqPoeYV39YnlZN5YNR 9XUstEZL iDXDIZZh1tp/R64gis0GXxlXj3GJ+fXJJvDDweN/FN0f29M6O+P7kyzsFiVT3GwuIS3TfUf5ohtu/5qF2avSfFDY1IW4l83wNIp0qQubcdML4s1YBZcyiYuZFgseExF9I6lr7 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 | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) diff --git a/mm/khugepaged.c b/mm/khugepaged.c index 8455a02dc3d6..ead07ccac351 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1435,10 +1435,39 @@ static int collapse_scan_bitmap(struct mm_struct *mm, unsigned long address, ret = collapse_huge_page(mm, address, referenced, unmapped, cc, mmap_locked, order, offset); - if (ret == SCAN_SUCCEED) { + + /* + * Analyze failure reason to determine next action: + * - goto next_order: try smaller orders in same region + * - continue: try other regions at same order + * - break: stop all attempts (system-wide failure) + */ + switch (ret) { + /* Cases were we should continue to the next region */ + case SCAN_SUCCEED: collapsed += 1UL << order; + 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; + /* All other cases should stop collapse attempts */ + default: + break; } + break; } next_order: -- 2.51.0