From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751960AbdHAOoz (ORCPT ); Tue, 1 Aug 2017 10:44:55 -0400 Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:60642 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751166AbdHAOox (ORCPT ); Tue, 1 Aug 2017 10:44:53 -0400 From: "Naveen N. Rao" To: Peter Zijlstra , Jiri Olsa , Arnaldo Carvalho de Melo , Ingo Molnar , Vince Weaver Cc: linux-kernel@vger.kernel.org Subject: [PATCH v2 0/2] Notifications for perf sideband events Date: Tue, 1 Aug 2017 20:14:02 +0530 X-Mailer: git-send-email 2.13.3 X-TM-AS-MML: disable x-cbid: 17080114-0012-0000-0000-000002585691 X-IBM-AV-DETECTION: SAVI=unused REMOTE=unused XFE=unused x-cbparentid: 17080114-0013-0000-0000-00000772CC6A Message-Id: X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2017-08-01_07:,, signatures=0 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 suspectscore=0 malwarescore=0 phishscore=0 adultscore=0 bulkscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.0.1-1706020000 definitions=main-1708010241 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org v2: - Patch 1: Some cosmetic updates to address Peter's feedback - Patch 2: Add unlikely() hint for test in __perf_output_begin() so as to minimize impact in normal cases. - Patch 2: Factor out handling of wakeup_events into a separate helper. This series has also been tested with perf_event_tests testsuite to ensure there are no regressions. - Naveen --- v1: https://www.mail-archive.com/linux-kernel@vger.kernel.org/msg1424933.html Currently, there is no way to ask for signals to be delivered when a certain number of sideband events have been logged into the ring buffer. This is problematic if we are only interested in, say, context switch events. Furthermore, signals are more useful (rather than polling) for self-profiling. This series provides for a way to achieve this. We ride on top of the existing support for ring buffer wakeup to generate signals as desired. Counting sideband events still requires some changes in the output path, but in normal cases, it ends up being just a comparison. The test program below demonstrates how a process can profile itself for context switch events and how it can control notification through signals. The key changes include the below perf_event_attr settings as well as use of IOC_ENABLE: pe.signal_on_wakeup = 1; pe.count_sb_events = 1; pe.wakeup_events = 2; To keep things simple, PERF_EVENT_IOC_REFRESH cannot be used if any of the new attributes are set. - Naveen --- Here is a sample program demonstrating the same: #define _GNU_SOURCE #include #include #include #include #include #include #include #include #include #include static long perf_event_open(struct perf_event_attr *hw_event, pid_t pid, int cpu, int group_fd, unsigned long flags) { return syscall(__NR_perf_event_open, hw_event, pid, cpu, group_fd, flags); } static void sigio_handler(int n, siginfo_t *info, void *uc) { fprintf (stderr, "Caught %s\n", info->si_code == POLL_HUP ? "POLL_HUP" : (info->si_code == POLL_IN ? "POLL_IN" : "other signal")); } int main(int argc, char **argv) { struct perf_event_attr pe; struct sigaction act; int fd; void *buf; memset(&act, 0, sizeof(act)); act.sa_sigaction = sigio_handler; act.sa_flags = SA_SIGINFO; sigaction(SIGIO, &act, 0); memset(&pe, 0, sizeof(struct perf_event_attr)); pe.size = sizeof(struct perf_event_attr); pe.type = PERF_TYPE_SOFTWARE; pe.config = PERF_COUNT_SW_DUMMY; pe.disabled = 1; pe.sample_period = 1; pe.context_switch = 1; pe.signal_on_wakeup = 1; pe.count_sb_events = 1; pe.wakeup_events = 2; fd = perf_event_open(&pe, 0, -1, -1, 0); if (fd == -1) { fprintf(stderr, "Error opening leader %lx\n", (unsigned long)pe.config); exit(EXIT_FAILURE); } buf = mmap(NULL, sysconf(_SC_PAGESIZE) * 2, PROT_READ|PROT_WRITE, MAP_SHARED, fd, 0); if (buf == MAP_FAILED) { fprintf(stderr, "Can't mmap buffer\n"); return -1; } if (fcntl(fd, F_SETFL, fcntl(fd, F_GETFL, 0) | O_ASYNC) == -1) return -2; if (fcntl(fd, F_SETSIG, SIGIO) == -1) return -3; if (fcntl(fd, F_SETOWN, getpid()) == -1) return -4; if (ioctl(fd, PERF_EVENT_IOC_ENABLE, 0) == -1) return -5; fprintf (stderr, "Sleep 1\n"); sleep(1); fprintf (stderr, "Sleep 2\n"); sleep(1); fprintf (stderr, "Sleep 3\n"); sleep(1); /* Disable the event counter */ ioctl(fd, PERF_EVENT_IOC_DISABLE, 1); close(fd); return 0; } A sample output: $ time ./cs Sleep 1 Caught POLL_IN Sleep 2 Caught POLL_IN Sleep 3 Caught POLL_IN real 0m3.040s user 0m0.001s sys 0m0.003s Naveen N. Rao (2): kernel/events: Add option to notify through signals on wakeup kernel/events: Add option to enable counting sideband events in wakeup_events include/uapi/linux/perf_event.h | 4 +++- kernel/events/core.c | 39 ++++++++++++++++++--------------------- kernel/events/internal.h | 1 + kernel/events/ring_buffer.c | 21 +++++++++++++++++++++ 4 files changed, 43 insertions(+), 22 deletions(-) -- 2.13.3