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Tue, 26 May 2020 22:09:51 +0000 From: Song Liu To: Steven Rostedt CC: Peter Zijlstra , linux-kernel , Kernel Team , Ingo Molnar , 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+yJPDqi65OeAgAACB4CAAAIsgIAAAuWAgAABdQA= Date: Tue, 26 May 2020 22:09:51 +0000 Message-ID: <196BAA45-AD7A-4DAE-A4C8-CED3DF2C6E17@fb.com> References: <20200526212826.4097888-1-songliubraving@fb.com> <20200526213913.GG2483@worktop.programming.kicks-ass.net> <20200526215415.GH2483@worktop.programming.kicks-ass.net> <20200526180437.45aed950@gandalf.local.home> In-Reply-To: <20200526180437.45aed950@gandalf.local.home> 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: goodmis.org; 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x-ms-exchange-antispam-messagedata: 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 Content-Type: text/plain; charset="us-ascii" Content-ID: <727EA5194B08C14EA1CD69904AAC3B11@namprd15.prod.outlook.com> Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-MS-Exchange-CrossTenant-Network-Message-Id: 03698b4a-fe29-4cd3-29d7-08d801c1831b X-MS-Exchange-CrossTenant-originalarrivaltime: 26 May 2020 22:09:51.1537 (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: pJiSXg6COIXps6JQXFYmm/vtLqHEvODJSPvRmjXV1WXnwjD2F3tdC2YLZa9qLA8f3xkT7kz59NneIvvps85YCA== X-MS-Exchange-Transport-CrossTenantHeadersStamped: BYAPR15MB3254 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 phishscore=0 clxscore=1015 adultscore=0 mlxscore=0 impostorscore=0 mlxlogscore=999 cotscore=-2147483648 spamscore=0 priorityscore=1501 suspectscore=0 bulkscore=0 malwarescore=0 lowpriorityscore=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 3:04 PM, Steven Rostedt wrote: >=20 > On Tue, 26 May 2020 23:54:15 +0200 > 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 wro= te: >>>>=20 >>>> On Tue, May 26, 2020 at 02:28:26PM -0700, Song Liu wrote: =20 >>>>> It is useful to trace functions in kernel/event/core.c. Allow ftrace = for >>>>> them by removing $(CC_FLAGS_FTRACE) from Makefile. =20 >>>>=20 >>>> Did you try using the ftrace event with perf with this on? =20 >>>=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 >>=20 >> I've no idea what probe: does. iirc there's something like >> ftrace:function that is like regular function tracing. >>=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. >=20 > In the early days there was a lot of issues with recursions, but I added = a > lot of recursion protection since then. I'll give this patch a spin and s= ee > if I can make it crash. Thanks!=20 Song=