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Thu, 8 Nov 2018 18:49:19 +0000 Received: from MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::4cd7:6768:136d:7a8b]) by MWHPR15MB1165.namprd15.prod.outlook.com ([fe80::4cd7:6768:136d:7a8b%2]) with mapi id 15.20.1294.034; Thu, 8 Nov 2018 18:49:19 +0000 From: Song Liu To: David Ahern CC: Peter Zijlstra , Netdev , lkml , Kernel Team , "ast@kernel.org" , "daniel@iogearbox.net" , "acme@kernel.org" Subject: Re: [RFC perf,bpf 1/5] perf, bpf: Introduce PERF_RECORD_BPF_EVENT Thread-Topic: [RFC perf,bpf 1/5] perf, bpf: Introduce PERF_RECORD_BPF_EVENT Thread-Index: AQHUdhLRNu0EDS9AC0KZ+9MuHYh4daVD/w6AgACjMoCAAVksAIAAM3wAgAAF/wCAAAZ1AA== Date: Thu, 8 Nov 2018 18:49:19 +0000 Message-ID: <050ABAC6-6C3B-4B6B-BB68-727127E00B51@fb.com> References: <20181106205246.567448-1-songliubraving@fb.com> <20181106205246.567448-2-songliubraving@fb.com> <20181107084057.GG9781@hirez.programming.kicks-ass.net> <31067290-4B66-4AA1-8027-607397BC0264@fb.com> <20181108150028.GU9761@hirez.programming.kicks-ass.net> In-Reply-To: Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3445.101.1) x-originating-ip: [2620:10d:c090:200::7:4fb8] x-ms-publictraffictype: Email x-microsoft-exchange-diagnostics: 1;MWHPR15MB1213;20:Kzv0u2XdA8ehZp4QbmqMsrZmjV8BD14x6ggg2grH7SCpaVFrli8tgIn9I9ug4LD8emg5NIQgFsP3yzKIdHAiwVtytnsVQ+l/xG2lhk9HBdHRoQ2g9rqTRfhbCGf11Wo9e9MNUGYpU5PurJwYwwo14y1VekenbYBJlj0t4XVM3+g= x-ms-exchange-antispam-srfa-diagnostics: SOS; x-ms-office365-filtering-correlation-id: 0cd1e35d-ea79-46a2-7b8b-08d645aae447 x-microsoft-antispam: BCL:0;PCL:0;RULEID:(7020095)(4652040)(8989299)(4534185)(4627221)(201703031133081)(201702281549075)(8990200)(5600074)(711020)(2017052603328)(7153060)(7193020);SRVR:MWHPR15MB1213; x-ms-traffictypediagnostic: MWHPR15MB1213: x-microsoft-antispam-prvs: x-exchange-antispam-report-test: UriScan:(85827821059158); x-ms-exchange-senderadcheck: 1 x-exchange-antispam-report-cfa-test: BCL:0;PCL:0;RULEID:(8211001083)(6040522)(2401047)(5005006)(8121501046)(823302103)(93006095)(93001095)(10201501046)(3002001)(3231382)(11241501184)(944501410)(52105095)(148016)(149066)(150057)(6041310)(20161123558120)(20161123564045)(20161123560045)(20161123562045)(201703131423095)(201702281528075)(20161123555045)(201703061421075)(201703061406153)(201708071742011)(7699051)(76991095);SRVR:MWHPR15MB1213;BCL:0;PCL:0;RULEID:;SRVR:MWHPR15MB1213; x-forefront-prvs: 0850800A29 x-forefront-antispam-report: SFV:NSPM;SFS:(10019020)(346002)(376002)(396003)(366004)(39860400002)(136003)(189003)(199004)(51444003)(1411001)(93886005)(36756003)(25786009)(105586002)(2906002)(106356001)(82746002)(478600001)(97736004)(86362001)(33656002)(6116002)(54906003)(57306001)(446003)(316002)(4326008)(5660300001)(14454004)(46003)(6436002)(6486002)(186003)(6512007)(256004)(50226002)(8676002)(305945005)(7736002)(81166006)(81156014)(8936002)(2616005)(6246003)(476003)(68736007)(486006)(2900100001)(11346002)(39060400002)(53936002)(102836004)(53546011)(6506007)(6916009)(83716004)(71190400001)(76176011)(99286004)(71200400001)(229853002)(142933001);DIR:OUT;SFP:1102;SCL:1;SRVR:MWHPR15MB1213;H:MWHPR15MB1165.namprd15.prod.outlook.com;FPR:;SPF:None;LANG:en;PTR:InfoNoRecords;MX:1;A:1; received-spf: None (protection.outlook.com: fb.com does not designate permitted sender hosts) x-microsoft-antispam-message-info: NA/4UqD6ChqCfcnrhp6PyhfDehRAlc70jeGzzaC4+dM8jVRy1/I2qwKJL5ObKxyu6fWhidN9W+FJJa2HlK1+RwHKs9wyuwx5WNUpOPqnBGmrXAOga00xjz9aiJfrkdMDt9sdhfG8U58AMHiYpwBM/K8vo/1XAyFgKlpghLdFZOFqHb2/UVHtCP6FBIYuYrfy2StPukrBPy0aHvuEegbm4Lnh04kMkBI85YqYSdcwXun2hFfMdSezgLmXWPyjxkSk5FIVRCdTSs3cbIb/oW0e+1B6Va/T28DWmwL9h3wlUmQI79gYIfDz3OBnidHFFKl5SdDupp7NxUsGwwEneAEQLAq/nKw/q8ToI8nQM30/erM= spamdiagnosticoutput: 1:99 spamdiagnosticmetadata: NSPM Content-Type: text/plain; charset="us-ascii" Content-ID: Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 0cd1e35d-ea79-46a2-7b8b-08d645aae447 X-MS-Exchange-CrossTenant-originalarrivaltime: 08 Nov 2018 18:49:19.3498 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 8ae927fe-1255-47a7-a2af-5f3a069daaa2 X-MS-Exchange-Transport-CrossTenantHeadersStamped: MWHPR15MB1213 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:,, definitions=2018-11-08_08:,, signatures=0 X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi David, > On Nov 8, 2018, at 10:26 AM, David Ahern wrote: >=20 > On 11/8/18 11:04 AM, Song Liu wrote: >> On the other hand, processing BPF load/unload events synchronously shoul= d >> not introduce too much overhead for meaningful use cases. If many BPF pr= ogs >> are being loaded/unloaded within short period of time, it is not the ste= ady >> state that profiling works care about.=20 >=20 > but, profiling is not the only use case, and perf-record is common with > those other use cases. >=20 > I think that answers why your RFC set does not fork a thread for the bpf > events. You are focused on profiling and for already loaded programs or > for a small number of programs loaded by a specific workload started by > perf. We sure can fork a thread for the BPF event. But I guess that's not Peter's main concern here... Could you please point me to more information about the use cases you worry= =20 about? I am more than happy to optimize the logic for those use cases.=20 Thanks, Song