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Tue, 26 May 2020 22:08:37 +0000 From: Song Liu To: Peter Zijlstra CC: linux-kernel , Kernel Team , Ingo Molnar , Steven Rostedt , Arnaldo Carvalho de Melo , "Masami Hiramatsu" , Mark Rutland , "Jiri Olsa" , Namhyung Kim , Alexey Budankov Subject: Re: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c Thread-Topic: [RFC] perf/core: allow ftrace for functions in kernel/event/core.c Thread-Index: AQHWM6ViVS5deg/n5kWgZSYX+yJPDqi65OeAgAACB4CAAAIsgIAABAOA Date: Tue, 26 May 2020 22:08:37 +0000 Message-ID: <226406AB-1245-4F4E-879C-B3B0320811DD@fb.com> References: <20200526212826.4097888-1-songliubraving@fb.com> <20200526213913.GG2483@worktop.programming.kicks-ass.net> <20200526215415.GH2483@worktop.programming.kicks-ass.net> In-Reply-To: <20200526215415.GH2483@worktop.programming.kicks-ass.net> Accept-Language: en-US Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-mailer: Apple Mail (2.3608.80.23.2.2) authentication-results: infradead.org; dkim=none (message not signed) header.d=none;infradead.org; 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x-ms-exchange-antispam-messagedata: nZX0pTOPUh1RNsIyxZQk1/F4LiYkgKdTGCDo7T7qFZWVJsj8Q5ar2DdMgjnkCrqsCqYH3cGjsBGppiK4pDEvw9NwFb9gkTGc9wleNuqtD4WCM3Qr2tIjlrqjhzRLGcHzNuRdrLa3vDIM3orm6ScQkrXC7e9R908nEgO5h0FVHlNQ76GdPJWmjyDUMxnEWW50I2zlpLX0L49P1Ot2YwieaESqAjCRA7O8DDrIFTM9m4dWj88NEnRQABefoPWy+mPYPxCP9v54tQGjs03X1I/mYZYTsraWNKuRPIfPZw9eC2ykNMe50YeNuZHHVdGO2f8rKupKy0VOFcCpnZNce1P2iUHko6Dza53+NEtLAYoWxNcpF8PL3ViYTPXf8W3qf3ckD8f5GU1dlswOiLTAnfGmwQ0F6qDG7I090v0A0YE2ZJv0dAhK5WpPT+zIoGZAVuE3llmJm7yxkFvuxgLu8AelBhfBmXdBvC/rhaWB6MVgEyu84ffFb4nXo6u6FjjUUMmbz9nP0EvDV2z1KIZyKGFA9g== Content-Type: text/plain; charset="us-ascii" Content-ID: <0CB12D5A4073D946B2F7E1764B231177@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 1ddd179c-52a1-43ef-f20b-08d801c1576a X-MS-Exchange-CrossTenant-originalarrivaltime: 26 May 2020 22:08:37.8288 (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: j2f6nC6Hiu7d1kdd6ZNMkIodVdeVHs77qeQUTAHj+f60PWvLIs8dH19r5b6zUBIPEOfdkZh0QQdypB5wk5OFyg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB2917 X-OriginatorOrg: fb.com X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.216,18.0.687 definitions=2020-05-26_02:2020-05-26,2020-05-26 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 suspectscore=0 spamscore=0 mlxscore=0 bulkscore=0 cotscore=-2147483648 mlxlogscore=999 phishscore=0 adultscore=0 priorityscore=1501 clxscore=1015 impostorscore=0 lowpriorityscore=0 malwarescore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2004280000 definitions=main-2005260171 X-FB-Internal: deliver Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > On May 26, 2020, at 2:54 PM, Peter Zijlstra wrote: >=20 > On Tue, May 26, 2020 at 09:46:29PM +0000, Song Liu wrote: >>=20 >>=20 >>> On May 26, 2020, at 2:39 PM, Peter Zijlstra wrot= e: >>>=20 >>> On Tue, May 26, 2020 at 02:28:26PM -0700, Song Liu wrote: >>>> It is useful to trace functions in kernel/event/core.c. Allow ftrace f= or >>>> them by removing $(CC_FLAGS_FTRACE) from Makefile. >>>=20 >>> Did you try using the ftrace event with perf with this on? >>=20 >> I have tried a few things, like=20 >>=20 >> perf stat -e probe:perf_read -I 1000 >> perf record -e probe:__x64_sys_perf_event_open -aR >>=20 >> They all work fine.=20 >>=20 >> Do you have some tricky functions that we should double check? >=20 > I've no idea what probe: does. iirc there's something like > ftrace:function that is like regular function tracing. Those are kprobes. I have CONFIG_HAVE_KPROBES_ON_FTRACE=3Dy in .config.=20 >=20 > At some point using that made the kernel really sick due to recursion > between ftrace and perf. Quite possibly that's been fixed, dunno. I also tried on ctx_sched_out() and event_sched_out(). They also work as expected.=20 Thanks, Song