From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 85800340DAB for ; Tue, 19 Aug 2025 13:45:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.133.124 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755611138; cv=none; b=rglpoRGAhpmOHwN1JHdRTxzfMtTX+AxjlPFZLmXS9l2Mv9t486VDPC7g9F8yA6Waj49qipiLq6vLmuDpoo44LZFdz+DYPUIfhCpmuXAGSwiTA4b8IoX65mZZggBf6QeEgLubh1YS9TyKW48DwfH295hAYIpXunmsklsFshCN658= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1755611138; c=relaxed/simple; bh=BcBkd2ONu3qEsJ8amjqoMv8e03xJ7JS1NkQC4inL7hY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=RXLnY9kAZS1KGu1l2gAzc9lyoQUb5z3nAYlbXWhsmRhLORIsHfrLHyHZWB4UMpibrzHvs0upKX4PgZ/CXg8emvziSMOeKMW1QrGKySpaXyHQlyaZAttx2IdXAxkQ5pgpraHEeEQN4RjQCH/Vz95urslTA6kvpHOsXNQI42I4yT4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=Vy/Lfhip; arc=none smtp.client-ip=170.10.133.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Vy/Lfhip" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1755611136; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=V5DchuEmH6POX8OSi9R3/H3ulGAsujcIoqxqs5qQqIk=; b=Vy/Lfhipd0Hxn6/3mcbGrg/LKB0HzdjFozDkEOQkaMXt0+QS4GoWxQ9Zxvf18mCSZ+DwlV iO0UnyxXuAE5KCDWpEP7B2LFO+aO65lkEOb9oMNxPhyPyajMLc8nR5c77x5jAaDdQD4Pwy vE5IhrDBHXD3tzXo5f+lVLjX7Z3sVD8= Received: from mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-682-kyYq5qvsNpunGuM_q3lK-Q-1; Tue, 19 Aug 2025 09:45:31 -0400 X-MC-Unique: kyYq5qvsNpunGuM_q3lK-Q-1 X-Mimecast-MFC-AGG-ID: kyYq5qvsNpunGuM_q3lK-Q_1755611126 Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 8979F180034D; Tue, 19 Aug 2025 13:45:26 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.137]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 3C00D19560BC; Tue, 19 Aug 2025 13:45:08 +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, kirill.shutemov@linux.intel.com, 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 Subject: [PATCH v10 08/13] khugepaged: avoid unnecessary mTHP collapse attempts Date: Tue, 19 Aug 2025 07:42:00 -0600 Message-ID: <20250819134205.622806-9-npache@redhat.com> In-Reply-To: <20250819134205.622806-1-npache@redhat.com> References: <20250819134205.622806-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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 6a4cf7e4a7cc..7d9b5100bea1 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1389,10 +1389,39 @@ 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 * KHUGEPAGED_MIN_MTHP_NR); - 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 += (1 << order); + case SCAN_PAGE_RO: + 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: -- 2.50.1