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Tue, 17 Nov 2020 20:56:19 +0000 Date: Tue, 17 Nov 2020 12:56:11 -0800 From: Martin KaFai Lau To: Dmitrii Banshchikov CC: , , , , , , , , , , , Subject: Re: [PATCH bpf-next] bpf: Add bpf_ktime_get_coarse_ns helper Message-ID: <20201117205611.mwvz7tt2lsczzdh5@kafai-mbp.dhcp.thefacebook.com> References: <20201117184549.257280-1-me@ubique.spb.ru> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20201117184549.257280-1-me@ubique.spb.ru> X-Originating-IP: [2620:10d:c090:400::5:603e] X-ClientProxiedBy: MWHPR1201CA0003.namprd12.prod.outlook.com (2603:10b6:301:4a::13) To BY5PR15MB3571.namprd15.prod.outlook.com (2603:10b6:a03:1f6::32) MIME-Version: 1.0 X-MS-Exchange-MessageSentRepresentingType: 1 Received: from kafai-mbp.dhcp.thefacebook.com (2620:10d:c090:400::5:603e) by MWHPR1201CA0003.namprd12.prod.outlook.com (2603:10b6:301:4a::13) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.3589.20 via Frontend Transport; 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X-MS-Exchange-AntiSpam-MessageData: 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 X-MS-Exchange-CrossTenant-Network-Message-Id: 92f54d7c-8434-48da-1dab-08d88b3b3b80 X-MS-Exchange-CrossTenant-AuthSource: BY5PR15MB3571.namprd15.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 17 Nov 2020 20:56:19.3386 (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: NfvCJmd7VnCrCTvgO0zGJeBtcmcMHBDw3z9NqlADsT/3nVWIlux63wpnqQcPoqsb X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2646 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.312,18.0.737 definitions=2020-11-17_09:2020-11-17,2020-11-17 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 clxscore=1011 mlxscore=0 spamscore=0 suspectscore=44 phishscore=0 adultscore=0 malwarescore=0 lowpriorityscore=0 impostorscore=0 priorityscore=1501 mlxlogscore=960 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2009150000 definitions=main-2011170154 X-FB-Internal: deliver Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org On Tue, Nov 17, 2020 at 06:45:49PM +0000, Dmitrii Banshchikov wrote: > The helper uses CLOCK_MONOTONIC_COARSE source of time that is less > accurate but more performant. > > We have a BPF CGROUP_SKB firewall that supports event logging through > bpf_perf_event_output(). Each event has a timestamp and currently we use > bpf_ktime_get_ns() for it. Use of bpf_ktime_get_coarse_ns() saves ~15-20 > ns in time required for event logging. > > bpf_ktime_get_ns(): > EgressLogByRemoteEndpoint 113.82ns 8.79M > bpf_ktime_get_coarse_ns(): > EgressLogByRemoteEndpoint 95.40ns 10.48M Acked-by: Martin KaFai Lau