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[209.132.180.67]) by mx.google.com with ESMTP id 84si32198668pfh.48.2016.01.25.00.40.02; Mon, 25 Jan 2016 00:40:03 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755849AbcAYIj5 (ORCPT + 30 others); Mon, 25 Jan 2016 03:39:57 -0500 Received: from szxga02-in.huawei.com ([119.145.14.65]:22286 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751403AbcAYIjZ (ORCPT ); Mon, 25 Jan 2016 03:39:25 -0500 Received: from 172.24.1.50 (EHLO SZXEML424-HUB.china.huawei.com) ([172.24.1.50]) by szxrg02-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id DAM37246; Mon, 25 Jan 2016 16:34:11 +0800 (CST) Received: from linux-4hy3.site (10.107.193.248) by SZXEML424-HUB.china.huawei.com (10.82.67.153) with Microsoft SMTP Server id 14.3.235.1; Mon, 25 Jan 2016 16:34:02 +0800 From: Wang Nan To: , , CC: , Wang Nan , He Kuang , Alexei Starovoitov , "Arnaldo Carvalho de Melo" , Brendan Gregg , "Jiri Olsa" , Masami Hiramatsu , Namhyung Kim , Zefan Li , Subject: [PATCH 3/5] perf core: Prepare writing into ring buffer from end Date: Mon, 25 Jan 2016 08:33:51 +0000 Message-ID: <1453710833-2865-4-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1453710833-2865-1-git-send-email-wangnan0@huawei.com> References: <1453710833-2865-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020204.56A5DEF1.0085, 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: 7354fec53f314b46c0b8b9a59c6e3d80 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Convert perf_output_begin to __perf_output_begin and make the later function able to write records from the end of the ring buffer. Following commits will utilize the 'backward' flag. This patch doesn't introduce any extra performance overhead since we use always_inline. 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 --- kernel/events/ring_buffer.c | 42 ++++++++++++++++++++++++++++++++++++------ 1 file changed, 36 insertions(+), 6 deletions(-) -- 1.8.3.4 diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index 9f1a93f..0684e880 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -102,8 +102,21 @@ out: preempt_enable(); } -int perf_output_begin(struct perf_output_handle *handle, - struct perf_event *event, unsigned int size) +static bool __always_inline +ring_buffer_has_space(unsigned long head, unsigned long tail, + unsigned long data_size, unsigned int size, + bool backward) +{ + if (!backward) + return CIRC_SPACE(head, tail, data_size) >= size; + else + return CIRC_SPACE(tail, head, data_size) >= size; +} + +static int __always_inline +__perf_output_begin(struct perf_output_handle *handle, + struct perf_event *event, unsigned int size, + bool backward) { struct ring_buffer *rb; unsigned long tail, offset, head; @@ -146,9 +159,12 @@ int perf_output_begin(struct perf_output_handle *handle, do { tail = READ_ONCE(rb->user_page->data_tail); offset = head = local_read(&rb->head); - if (!rb->overwrite && - unlikely(CIRC_SPACE(head, tail, perf_data_size(rb)) < size)) - goto fail; + if (!rb->overwrite) { + if (unlikely(!ring_buffer_has_space(head, tail, + perf_data_size(rb), + size, backward))) + goto fail; + } /* * The above forms a control dependency barrier separating the @@ -162,9 +178,17 @@ int perf_output_begin(struct perf_output_handle *handle, * See perf_output_put_handle(). */ - head += size; + if (!backward) + head += size; + else + head -= size; } while (local_cmpxchg(&rb->head, offset, head) != offset); + if (backward) { + offset = head; + head = (u64)(-head); + } + /* * We rely on the implied barrier() by local_cmpxchg() to ensure * none of the data stores below can be lifted up by the compiler. @@ -206,6 +230,12 @@ out: return -ENOSPC; } +int perf_output_begin(struct perf_output_handle *handle, + struct perf_event *event, unsigned int size) +{ + return __perf_output_begin(handle, event, size, false); +} + unsigned int perf_output_copy(struct perf_output_handle *handle, const void *buf, unsigned int len) {