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 4A97F34D4CE for ; Wed, 22 Oct 2025 18:40:40 +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=1761158442; cv=none; b=f2bH89o8ojKeR2OWC2Czk7+A0iVrQNq1ExqxPqgbVT0QPkHWCQVyBJgNtG1mvdQH9Uw+UQE0AjuYf7YiMvqGptt/0lhAMGIF5XPEeBehfiR9+Ked8Eajp7WR6yb0bux424u792WXAhiiseT295Zc1WdgT9gGTKaLQqNRpR1d7tE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761158442; c=relaxed/simple; bh=U9V8WUau2xvb5m+qTTde+ND4eWcCue0wfexMllB7HJg=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=l2DbsO70AvlGg6qKzB22K7NOiqIn8xc0fDTKe6VTTEKzGDbIGfCFXHG0T2KS3b6ZxDMGpTe28SQ/oIPExjDrM7j05eaYZfk6Uh1pZl3RIb8huUrKo8I6BQdaYmreyHZfx/uiVpc9EgU0rjul4CvOu+MxyaysCEpAIIo/vgNIvNo= 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=C3SqrYvR; 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="C3SqrYvR" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1761158439; 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=+jXNuiQ5bHnX5LcOt47Wp1opTjuPzrwwutPcN/KCqFQ=; b=C3SqrYvRtl2QnLR/+4sldXQD5rg1eMXwA0zXWz1OtjfUBewMlP2bY4hAWaibu/0Kav1Zk+ hoDLJBenB5a8HlOj+Bfh2TjCFqlONdXmTPHxFGNrLIayO04QbA2453PSsSxxyUmvVkFUyr nGIlqw3MRcdcVOQOobZS93VyI9QxudU= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-668-IY3uYX_EMg2HzlP-YAxfIw-1; Wed, 22 Oct 2025 14:40:35 -0400 X-MC-Unique: IY3uYX_EMg2HzlP-YAxfIw-1 X-Mimecast-MFC-AGG-ID: IY3uYX_EMg2HzlP-YAxfIw_1761158430 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-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id A54B819560A7; Wed, 22 Oct 2025 18:40:30 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.64.41]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 79C9F19560B4; Wed, 22 Oct 2025 18:40:21 +0000 (UTC) From: Nico Pache To: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@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 v12 mm-new 13/15] khugepaged: avoid unnecessary mTHP collapse attempts Date: Wed, 22 Oct 2025 12:37:15 -0600 Message-ID: <20251022183717.70829-14-npache@redhat.com> In-Reply-To: <20251022183717.70829-1-npache@redhat.com> References: <20251022183717.70829-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-doc@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 e2319bfd0065..54f5c7888e46 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1431,10 +1431,39 @@ 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