Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932095AbcCaJ1T (ORCPT ); Thu, 31 Mar 2016 05:27:19 -0400 Received: from terminus.zytor.com ([198.137.202.10]:38214 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756516AbcCaJ1O (ORCPT ); Thu, 31 Mar 2016 05:27:14 -0400 Date: Thu, 31 Mar 2016 02:26:05 -0700 From: tip-bot for Wang Nan Message-ID: Cc: jolsa@kernel.org, acme@redhat.com, namhyung@kernel.org, masami.hiramatsu.pt@hitachi.com, jolsa@redhat.com, torvalds@linux-foundation.org, eranian@google.com, pi3orama@163.com, ast@kernel.org, tglx@linutronix.de, mingo@kernel.org, alexander.shishkin@linux.intel.com, wangnan0@huawei.com, hpa@zytor.com, brendan.d.gregg@gmail.com, lizefan@huawei.com, vincent.weaver@maine.edu, peterz@infradead.org, hekuang@huawei.com, linux-kernel@vger.kernel.org Reply-To: mingo@kernel.org, tglx@linutronix.de, alexander.shishkin@linux.intel.com, wangnan0@huawei.com, hpa@zytor.com, brendan.d.gregg@gmail.com, lizefan@huawei.com, vincent.weaver@maine.edu, peterz@infradead.org, linux-kernel@vger.kernel.org, hekuang@huawei.com, jolsa@kernel.org, masami.hiramatsu.pt@hitachi.com, jolsa@redhat.com, acme@redhat.com, namhyung@kernel.org, torvalds@linux-foundation.org, eranian@google.com, pi3orama@163.com, ast@kernel.org In-Reply-To: <1459147292-239310-2-git-send-email-wangnan0@huawei.com> References: <1459147292-239310-2-git-send-email-wangnan0@huawei.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf/ring_buffer: Introduce new ioctl options to pause and resume the ring-buffer Git-Commit-ID: 86e7972f690c1017fd086cdfe53d8524e68c661c X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4828 Lines: 142 Commit-ID: 86e7972f690c1017fd086cdfe53d8524e68c661c Gitweb: http://git.kernel.org/tip/86e7972f690c1017fd086cdfe53d8524e68c661c Author: Wang Nan AuthorDate: Mon, 28 Mar 2016 06:41:29 +0000 Committer: Ingo Molnar CommitDate: Thu, 31 Mar 2016 10:30:45 +0200 perf/ring_buffer: Introduce new ioctl options to pause and resume the ring-buffer Add new ioctl() to pause/resume ring-buffer output. In some situations we want to read from the ring-buffer only when we ensure nothing can write to the ring-buffer during reading. Without this patch we have to turn off all events attached to this ring-buffer to achieve this. This patch is a prerequisite to enable overwrite support for the perf ring-buffer support. Following commits will introduce new methods support reading from overwrite ring buffer. Before reading, caller must ensure the ring buffer is frozen, or the reading is unreliable. Signed-off-by: Wang Nan Signed-off-by: Peter Zijlstra (Intel) Cc: Cc: Alexander Shishkin Cc: Alexei Starovoitov Cc: Arnaldo Carvalho de Melo Cc: Brendan Gregg Cc: He Kuang Cc: Jiri Olsa Cc: Jiri Olsa Cc: Linus Torvalds Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Stephane Eranian Cc: Thomas Gleixner Cc: Vince Weaver Cc: Zefan Li Link: http://lkml.kernel.org/r/1459147292-239310-2-git-send-email-wangnan0@huawei.com Signed-off-by: Ingo Molnar --- include/uapi/linux/perf_event.h | 1 + kernel/events/core.c | 13 +++++++++++++ kernel/events/internal.h | 9 +++++++++ kernel/events/ring_buffer.c | 12 +++++++++++- 4 files changed, 34 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/perf_event.h b/include/uapi/linux/perf_event.h index 1afe962..a3c1903 100644 --- a/include/uapi/linux/perf_event.h +++ b/include/uapi/linux/perf_event.h @@ -401,6 +401,7 @@ struct perf_event_attr { #define PERF_EVENT_IOC_SET_FILTER _IOW('$', 6, char *) #define PERF_EVENT_IOC_ID _IOR('$', 7, __u64 *) #define PERF_EVENT_IOC_SET_BPF _IOW('$', 8, __u32) +#define PERF_EVENT_IOC_PAUSE_OUTPUT _IOW('$', 9, __u32) enum perf_event_ioc_flags { PERF_IOC_FLAG_GROUP = 1U << 0, diff --git a/kernel/events/core.c b/kernel/events/core.c index 243df4b..51386e8 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4379,6 +4379,19 @@ static long _perf_ioctl(struct perf_event *event, unsigned int cmd, unsigned lon case PERF_EVENT_IOC_SET_BPF: return perf_event_set_bpf_prog(event, arg); + case PERF_EVENT_IOC_PAUSE_OUTPUT: { + struct ring_buffer *rb; + + rcu_read_lock(); + rb = rcu_dereference(event->rb); + if (!rb || !rb->nr_pages) { + rcu_read_unlock(); + return -EINVAL; + } + rb_toggle_paused(rb, !!arg); + rcu_read_unlock(); + return 0; + } default: return -ENOTTY; } diff --git a/kernel/events/internal.h b/kernel/events/internal.h index 2b229fd..2d67327 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -17,6 +17,7 @@ struct ring_buffer { #endif int nr_pages; /* nr of data pages */ int overwrite; /* can overwrite itself */ + int paused; /* can write into ring buffer */ atomic_t poll; /* POLL_ for wakeups */ @@ -64,6 +65,14 @@ static inline void rb_free_rcu(struct rcu_head *rcu_head) rb_free(rb); } +static inline void rb_toggle_paused(struct ring_buffer *rb, bool pause) +{ + if (!pause && rb->nr_pages) + rb->paused = 0; + else + rb->paused = 1; +} + extern struct ring_buffer * rb_alloc(int nr_pages, long watermark, int cpu, int flags); extern void perf_event_wakeup(struct perf_event *event); diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 0ed4555..72d8127 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -125,8 +125,11 @@ int perf_output_begin(struct perf_output_handle *handle, if (unlikely(!rb)) goto out; - if (unlikely(!rb->nr_pages)) + if (unlikely(rb->paused)) { + if (rb->nr_pages) + local_inc(&rb->lost); goto out; + } handle->rb = rb; handle->event = event; @@ -241,6 +244,13 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); + + /* + * perf_output_begin() only checks rb->paused, therefore + * rb->paused must be true if we have no pages for output. + */ + if (!rb->nr_pages) + rb->paused = 1; } /*