Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754642AbcC1Gmq (ORCPT ); Mon, 28 Mar 2016 02:42:46 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:31641 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752924AbcC1Gma (ORCPT ); Mon, 28 Mar 2016 02:42:30 -0400 From: Wang Nan To: Alexei Starovoitov , Arnaldo Carvalho de Melo , Peter Zijlstra CC: , Brendan Gregg , He Kuang , Jiri Olsa , Masami Hiramatsu , Namhyung Kim , , Wang Nan , Zefan Li Subject: [PATCH 1/4] perf core: Introduce new ioctl options to pause and resume ring buffer Date: Mon, 28 Mar 2016 06:41:29 +0000 Message-ID: <1459147292-239310-2-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1459147292-239310-1-git-send-email-wangnan0@huawei.com> References: <1459147292-239310-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.56F8D246.0102,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-06-18 04:22:30, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: 0770becd6fd424f58903b18a9485eca8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3896 Lines: 123 Add new ioctl() to pause/resume ring-buffer output. In some situations we want to read from 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 for supporting overwrite ring buffer. 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 Cc: He Kuang Cc: Alexei Starovoitov Cc: Arnaldo Carvalho de Melo Cc: Brendan Gregg Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com --- include/uapi/linux/perf_event.h | 1 + kernel/events/core.c | 13 +++++++++++++ kernel/events/internal.h | 11 +++++++++++ kernel/events/ring_buffer.c | 7 ++++++- 4 files changed, 31 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 de24fbc..cb47da3 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -4341,6 +4341,19 @@ 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 (!event->rb) { + 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 2bbad9c..6a93d1b 100644 --- a/kernel/events/internal.h +++ b/kernel/events/internal.h @@ -18,6 +18,7 @@ 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 */ @@ -65,6 +66,16 @@ 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 c61f0cb..17de83b 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; @@ -244,6 +247,8 @@ ring_buffer_init(struct ring_buffer *rb, long watermark, int flags) INIT_LIST_HEAD(&rb->event_list); spin_lock_init(&rb->event_lock); init_irq_work(&rb->irq_work, rb_irq_work); + + rb->paused = rb->nr_pages ? 0 : 1; } static void ring_buffer_put_async(struct ring_buffer *rb) -- 1.8.3.4