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Miller" , Eric Dumazet , Jakub Kicinski , Paolo Abeni , "linux-kernel@vger.kernel.org" Subject: Re: [PATCH v2 net] net: enetc: survive memory pressure without crashing Thread-Topic: [PATCH v2 net] net: enetc: survive memory pressure without crashing Thread-Index: AQHY6TRiZQ8LCqV8m0qJGRg70aV0FK4h0giAgAB6WYA= Date: Thu, 27 Oct 2022 14:21:26 +0000 Message-ID: <20221027142125.k27ns6yan4rmxmwo@skbuf> References: <20221026121330.2042989-1-vladimir.oltean@nxp.com> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: authentication-results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nxp.com; x-ms-publictraffictype: Email x-ms-traffictypediagnostic: VI1PR04MB5136:EE_|AS4PR04MB9314:EE_ x-ms-office365-filtering-correlation-id: 47756865-710e-4393-f94f-08dab8268869 x-ms-exchange-senderadcheck: 1 x-ms-exchange-antispam-relay: 0 x-microsoft-antispam: BCL:0; x-microsoft-antispam-message-info: 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 x-forefront-antispam-report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:VI1PR04MB5136.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230022)(4636009)(7916004)(366004)(346002)(376002)(136003)(396003)(39860400002)(451199015)(41300700001)(71200400001)(64756008)(66946007)(316002)(66476007)(76116006)(66446008)(54906003)(4326008)(478600001)(6486002)(4744005)(8676002)(5660300002)(66556008)(44832011)(38070700005)(6862004)(2906002)(86362001)(33716001)(26005)(1076003)(122000001)(6506007)(38100700002)(186003)(9686003)(6636002)(6512007)(8936002);DIR:OUT;SFP:1101; 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charset="us-ascii" Content-ID: <82BD10F6F066204B974DF37AB0D10706@eurprd04.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: nxp.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5136.eurprd04.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 47756865-710e-4393-f94f-08dab8268869 X-MS-Exchange-CrossTenant-originalarrivaltime: 27 Oct 2022 14:21:26.3104 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 686ea1d3-bc2b-4c6f-a92c-d99c5c301635 X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: 9O843OJKgE80S7L428b9pia3o9cV2YP+0ere1Yc5HpsOOJi+8BzNXG9ONFs9JgCTeE6lFtKs8HAREQ13v2Zt/w== X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS4PR04MB9314 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Thu, Oct 27, 2022 at 07:03:31AM +0000, Claudiu Manoil wrote: > How do you trigger this "extreme case of memory pressure" where no enetc = buffer > can be allocated? Do you simulate it? As far as I understand, making dev_alloc_page() predictably fail in some particular spot is hard and probabilistic (but possible given enough tries)= . The reason I stubled upon this particularly bad handling of low memory in the enetc driver is because with AF_XDP zero-copy sockets, memory for RX buffers comes directly from user space, which may simply opt to not put any buffers in the fill queue (see "xdpsock --txonly" for example). The fix for the case where the buffers come from the kernel's page allocator is simply analogous to that. It would be shady to add this exact same patch only as part of the XSK work, when it's clear that existing code suffers from this problem too, even if it's not easy to trigger it.=