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Fri, 13 Nov 2020 19:40:28 +0000 Date: Fri, 13 Nov 2020 11:40:23 -0800 From: Roman Gushchin To: Song Liu CC: bpf , Alexei Starovoitov , Daniel Borkmann , "netdev@vger.kernel.org" , Andrii Nakryiko , Shakeel Butt , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , Kernel Team Subject: Re: [PATCH bpf-next v5 06/34] bpf: prepare for memcg-based memory accounting for bpf maps Message-ID: <20201113194023.GD2955309@carbon.dhcp.thefacebook.com> References: <20201112221543.3621014-1-guro@fb.com> <20201112221543.3621014-7-guro@fb.com> <3645417A-F356-4422-B336-874DFEB74014@fb.com> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3645417A-F356-4422-B336-874DFEB74014@fb.com> X-Originating-IP: [2620:10d:c090:400::5:7f67] X-ClientProxiedBy: MW3PR05CA0002.namprd05.prod.outlook.com (2603:10b6:303:2b::7) To SN6PR1501MB4141.namprd15.prod.outlook.com (2603:10b6:805:e3::14) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from carbon.dhcp.thefacebook.com (2620:10d:c090:400::5:7f67) by MW3PR05CA0002.namprd05.prod.outlook.com (2603:10b6:303:2b::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3564.21 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 203f1137-de98-45a2-29c3-08d8880bf989 X-MS-Exchange-CrossTenant-AuthSource: SN6PR1501MB4141.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 13 Nov 2020 19:40:28.7018 (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: ZmVz8xg1eM5zjwiVgLLsMth3752goZiIn0FUovRr2s9TBpS/XySnv+d+29NCRAc4 X-MS-Exchange-Transport-CrossTenantHeadersStamped: SN6PR1501MB2191 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-13_17:2020-11-13,2020-11-13 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 mlxlogscore=798 lowpriorityscore=0 impostorscore=0 malwarescore=0 clxscore=1015 adultscore=0 phishscore=0 spamscore=0 bulkscore=0 mlxscore=0 suspectscore=1 priorityscore=1501 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011130127 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Fri, Nov 13, 2020 at 09:46:49AM -0800, Song Liu wrote: > > > > On Nov 12, 2020, at 2:15 PM, Roman Gushchin wrote: > > [...] > > > > > +#ifdef CONFIG_MEMCG_KMEM > > +static __always_inline int __bpf_map_update_elem(struct bpf_map *map, void *key, > > + void *value, u64 flags) > > +{ > > + struct mem_cgroup *old_memcg; > > + bool in_interrupt; > > + int ret; > > + > > + /* > > + * If update from an interrupt context results in a memory allocation, > > + * the memory cgroup to charge can't be determined from the context > > + * of the current task. Instead, we charge the memory cgroup, which > > + * contained a process created the map. > > + */ > > + in_interrupt = in_interrupt(); > > + if (in_interrupt) > > + old_memcg = set_active_memcg(map->memcg); > > set_active_memcg() checks in_interrupt() again. Maybe we can introduce another > helper to avoid checking it twice? Something like > > static inline struct mem_cgroup * > set_active_memcg_int(struct mem_cgroup *memcg) > { > struct mem_cgroup *old; > > old = this_cpu_read(int_active_memcg); > this_cpu_write(int_active_memcg, memcg); > return old; > } Yeah, it's a good idea! in_interrupt() check is very cheap (like checking some bits in a per-cpu variable), so I don't think there will be any measurable difference. So I suggest to implement it later as an enhancement on top (maybe in the next merge window), to avoid an another delay. Otherwise I'll need to send a patch to mm@, wait for reviews and an inclusion into the mm tree, etc). Does it work for you? Thanks!