Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Date:   Thu, 21 May 2020 14:14:14 -0700
From:   Roman Gushchin <guro@fb.com>
To:     Vlastimil Babka <vbabka@suse.cz>
CC:     Andrew Morton <akpm@linux-foundation.org>,
        Johannes Weiner <hannes@cmpxchg.org>,
        Michal Hocko <mhocko@kernel.org>, <linux-mm@kvack.org>,
        <kernel-team@fb.com>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v3 03/19] mm: memcg: convert vmstat slab counters to bytes
Message-ID: <20200521211414.GB339999@carbon.DHCP.thefacebook.com>
References: <20200422204708.2176080-1-guro@fb.com>
 <20200422204708.2176080-4-guro@fb.com>
 <b72ff85a-22aa-f55d-41ee-2ddee00674a7@suse.cz>
 <20200520192652.GA278395@carbon.dhcp.thefacebook.com>
 <21975f76-f58f-14ef-9547-7e32afac1681@suse.cz>
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <21975f76-f58f-14ef-9547-7e32afac1681@suse.cz>
MIME-Version: 1.0
X-MS-Exchange-MessageSentRepresentingType: 1
Received: from carbon.DHCP.thefacebook.com (2620:10d:c090:400::5:edd) by BY5PR20CA0033.namprd20.prod.outlook.com (2603:10b6:a03:1f4::46) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3021.24 via Frontend Transport; Thu, 21 May 2020 21:14:17 +0000
X-Originating-IP: [2620:10d:c090:400::5:edd]
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: ce924f10-e641-447c-c519-08d7fdcbec1d
X-MS-TrafficTypeDiagnostic: BYAPR15MB4101:
X-MS-Exchange-Transport-Forked: True
X-Microsoft-Antispam-PRVS: <BYAPR15MB4101C90E69A2A9E6C066A9C6BEB70@BYAPR15MB4101.namprd15.prod.outlook.com>
X-FB-Source: Internal
X-MS-Oob-TLC-OOBClassifiers: OLM:7691;
X-Forefront-PRVS: 041032FF37
X-MS-Exchange-SenderADCheck: 1
X-Microsoft-Antispam: BCL:0;
X-Microsoft-Antispam-Message-Info: Ho2tIswiXi0yi3XJims7nOKVWxH/nKECSZMSYnIGJ+D8D2NP2S4of/zvc+GWdOteHEipLHM85OQ8jwsSqan+AxdTIjjWvbpSO/t1B07cx7XAaQcnvDNJqWGU866zgOVA0O2sCfEIg9OU55EDPPenwmLSCnZQbK+/87Q+rh6NgGXN7kPktEh0BiDrzsXTgD1aczew09AscsJanLb9+qXZApyNHx+8xanTZiOLQbC8RQ0x4WDRiZ1w86EMUnq4+POHden24v/5JjV0N6az8mozL8d27/J46ZgbNo3m9UvnfesISdqbKf1vAEayoPb8jkG1YY+5KhZ6o9SevZ+Ia+hUYA==
X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:BYAPR15MB4136.namprd15.prod.outlook.com;PTR:;CAT:NONE;SFTY:;SFS:(346002)(396003)(39860400002)(136003)(366004)(376002)(53546011)(52116002)(16526019)(8936002)(316002)(8676002)(7696005)(478600001)(4326008)(86362001)(33656002)(54906003)(9686003)(55016002)(1076003)(6666004)(6506007)(186003)(6916009)(66556008)(5660300002)(66476007)(2906002)(66946007);DIR:OUT;SFP:1102;
X-MS-Exchange-AntiSpam-MessageData: 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
X-MS-Exchange-CrossTenant-Network-Message-Id: ce924f10-e641-447c-c519-08d7fdcbec1d
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 May 2020 21:14:17.9855
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: PLJU41cHuu7j9GGfC4rWJBf3n741eKD7/0YXxDCCurxOY26m5ciqZUKpOlUA5j/v
X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB4101
X-OriginatorOrg: fb.com
X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.676
 definitions=2020-05-21_14:2020-05-21,2020-05-21 signatures=0
X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 lowpriorityscore=0
 spamscore=0 mlxscore=0 malwarescore=0 adultscore=0 mlxlogscore=872
 impostorscore=0 bulkscore=0 cotscore=-2147483648 phishscore=0
 priorityscore=1501 suspectscore=1 clxscore=1015 classifier=spam adjust=0
 reason=mlx scancount=1 engine=8.12.0-2004280000
 definitions=main-2005210158
X-FB-Internal: deliver
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, May 21, 2020 at 11:57:12AM +0200, Vlastimil Babka wrote:
> On 5/20/20 9:26 PM, Roman Gushchin wrote:
> > On Wed, May 20, 2020 at 02:25:22PM +0200, Vlastimil Babka wrote:
> >> 
> >> However __mod_node_page_state() and mode_node_state() will now branch always. I
> >> wonder if the "API clean" goal is worth it...
> > 
> > You mean just adding a special write-side helper which will perform a conversion
> > and put VM_WARN_ON_ONCE() into generic write-side helpers?
> 
> What I mean is that maybe node/global helpers should assume page granularity,
> and lruvec/memcg helpers do the check is they should convert from bytes to pages
> when calling node/global helpers. Then there would be no extra branches in
> node/global helpers. But maybe it's not worth saving those branches, dunno.

The problem is with helpers like mod_lruvec_state(), which do modify both global
and memcg-level counters. Also memcg- and global counters share idxes, so
it will be confusing to have NR_SLAB_RECLAIMABLE in bytes on one level and
in pages on the other.

So, idk, maybe there is a better way of organizing these counters in a less
complicated manner, but I've no ideas at the moment. But if you do, I'll appreciate it.

Thanks!