From nobody Mon Dec 1 21:30:06 2025 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 BDD8133A6EC for ; Mon, 1 Dec 2025 17:49:54 +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=1764611396; cv=none; b=sYSjCtUsG/fXt8SXhEwsImodxLRbxmnSeFn6Jrpf6vvG8JZlgCchiQrBuPC9iLAb1wPobbCqCHfEchMqAnu6O0VAnBdkib5ZVOqfUIa2UU5/S15hPGMbm2VKHwzSy1Ve3CzJQ8LArM44Ryw8fNfjRKBJPZ58V06aThnNvPHzW1U= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1764611396; c=relaxed/simple; bh=MP+0/APcroTtTHLnLx/nuOxFWSRLx5a31u2gSOYIhTs=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=erUbhpyO/sEhkaxLQOyxtXxGROiMRsr11aFYA3dibOg+NGyUio+XvzlsEwO21m9SZ57UXcDE4BUQeVwV6ecjSzMAQKt6aBDr2M5jcDjAmORqF0cyc+F+cgajzssxIHWN12OXIFoLKw5W0R2AO+fCWocC3KHqv2NI49c1RR/v4dk= 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=hDCt5K3g; 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="hDCt5K3g" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1764611393; 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=7ShTcDLxXyZs/NuRdOzDyMIIPzg+5zGuWDXBHW57k34=; b=hDCt5K3g0wonRQDNW6iiXZ8hjQhX5FEzNCVOCi0xqa2u0pfPlu8QZd3dY2n5xcx22o3sg4 Z1EwzjEGzsqzbsqMFRjckysTfdhAATQYLZDWLFpW01EpP4EL8RP5FEmzzsfZ8T+O/P6t2K ZZcOjofl+X4HUGUT9in72vQRs0EX3Cc= Received: from mx-prod-mc-03.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-590-17XU2vohN7OLwRxYhfKiNg-1; Mon, 01 Dec 2025 12:49:50 -0500 X-MC-Unique: 17XU2vohN7OLwRxYhfKiNg-1 X-Mimecast-MFC-AGG-ID: 17XU2vohN7OLwRxYhfKiNg_1764611385 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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id AFE881955F2A; Mon, 1 Dec 2025 17:49:45 +0000 (UTC) Received: from h1.redhat.com (unknown [10.22.66.60]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 06CED1800361; Mon, 1 Dec 2025 17:49:35 +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 v13 mm-new 14/16] khugepaged: avoid unnecessary mTHP collapse attempts Date: Mon, 1 Dec 2025 10:46:25 -0700 Message-ID: <20251201174627.23295-15-npache@redhat.com> In-Reply-To: <20251201174627.23295-1-npache@redhat.com> References: <20251201174627.23295-1-npache@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" 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 fcb927cd5456..daf39aab7e86 100644 --- a/mm/khugepaged.c +++ b/mm/khugepaged.c @@ -1503,9 +1503,42 @@ static int mthp_collapse(struct mm_struct *mm, unsig= ned long address, ret =3D collapse_huge_page(mm, collapse_address, referenced, unmapped, cc, mmap_locked, order); - if (ret =3D=3D SCAN_SUCCEED) { + + switch (ret) { + /* Cases were we continue to next collapse candidate */ + case SCAN_SUCCEED: collapsed +=3D 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; } } =20 --=20 2.51.1