From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-119.freemail.mail.aliyun.com (out30-119.freemail.mail.aliyun.com [115.124.30.119]) (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 1224C1B5EB5; Wed, 30 Apr 2025 10:12:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.119 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746007968; cv=none; b=pzQ+mVJFMdYpPe77gzNtVoX7OVtAOP1reEuNdfBAJWF4NrjUQOrHj0Ijb1cP8IuZrCqCi3ftv81jHEIhVFyt+2PV0dtqtbb6rqsRRloww2mAyUzsmEMsWl6scl2VBKJi6gLq27oDH+oNSr2AaXckV6M/pazIl7+rhk4LSExe1F8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1746007968; c=relaxed/simple; bh=bSbjHd5fpmwuxfDGYWijAmxsLNypiafgTKyiPu9nVsY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LHGNnHL4okktSGKu7E1LinNozd4+yyjgeU26ZbwJZne9UTjnVUXtl4GqtGBM/sxJkYYg5+hSkhsY4BET3RmeZi2rGetNRvD+ZBkURxF9LxL+bbt26C3Nn++pc28VFlYVIzjDoMAQ2qAOIspQT4hQTCFMFJuMomf5UtnDuIEYgM8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=OvV51h+L; arc=none smtp.client-ip=115.124.30.119 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="OvV51h+L" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1746007957; h=Message-ID:Date:MIME-Version:Subject:To:From:Content-Type; bh=jWF4Fc/9faHdX2BfnWYsn6epFHIXAYKUNdSnF1XgcMQ=; b=OvV51h+LHWRbSC4cTIToEvPpbDzomXgEftvwug39L+n5/OJxF30Pl3yhZ3HRE5QkJhj9X6MemjHVYaA93zUts3YaFP1OmadiNcL+BzlWu5Gm4Nv3988JHQsGVKfhOQnGnMgEpHfQqXLhi7xkBY2c28NM4YvNCqnjt9Firz+EUuw= Received: from 30.74.146.9(mailfrom:baolin.wang@linux.alibaba.com fp:SMTPD_---0WYoKRf3_1746007953 cluster:ay36) by smtp.aliyun-inc.com; Wed, 30 Apr 2025 18:12:34 +0800 Message-ID: Date: Wed, 30 Apr 2025 18:12:33 +0800 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 09/12] khugepaged: avoid unnecessary mTHP collapse attempts To: Nico Pache , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org Cc: akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.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, dev.jain@arm.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, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com References: <20250428181218.85925-1-npache@redhat.com> <20250428181218.85925-10-npache@redhat.com> From: Baolin Wang In-Reply-To: <20250428181218.85925-10-npache@redhat.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 2025/4/29 02:12, Nico Pache wrote: > 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 | 17 +++++++++++++++++ > 1 file changed, 17 insertions(+) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 86d1153ce9e8..5e6732cccb86 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -1365,6 +1365,23 @@ static int khugepaged_scan_bitmap(struct mm_struct *mm, unsigned long address, > collapsed += (1 << order); > continue; > } > + /* > + * Some ret values indicate all lower order will also > + * fail, dont trying to collapse smaller orders > + */ > + if (ret == SCAN_EXCEED_NONE_PTE || > + ret == SCAN_EXCEED_SWAP_PTE || > + ret == SCAN_EXCEED_SHARED_PTE || > + ret == SCAN_PTE_NON_PRESENT || > + ret == SCAN_PTE_UFFD_WP || > + ret == SCAN_ALLOC_HUGE_PAGE_FAIL || > + ret == SCAN_CGROUP_CHARGE_FAIL || > + ret == SCAN_COPY_MC || > + ret == SCAN_PAGE_LOCK || > + ret == SCAN_PAGE_COUNT) > + goto next; > + else > + break; Better to merge this patch into patch 6, which can be helped to understand your logic.