From patchwork Mon May 23 07:13:40 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Wang Nan X-Patchwork-Id: 68332 Delivered-To: patch@linaro.org Received: by 10.140.92.199 with SMTP id b65csp1073517qge; Mon, 23 May 2016 00:16:39 -0700 (PDT) X-Received: by 10.66.169.8 with SMTP id aa8mr14131790pac.85.1463987798932; Mon, 23 May 2016 00:16:38 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id d28si4826755pfj.62.2016.05.23.00.16.38; Mon, 23 May 2016 00:16:38 -0700 (PDT) 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 S1753329AbcEWHOy (ORCPT + 30 others); Mon, 23 May 2016 03:14:54 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:38519 "EHLO szxga02-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753289AbcEWHOu (ORCPT ); Mon, 23 May 2016 03:14:50 -0400 Received: from 172.24.1.60 (EHLO szxeml432-hub.china.huawei.com) ([172.24.1.60]) by szxrg02-dlp.huawei.com (MOS 4.3.7-GA FastPath queued) with ESMTP id DHM41863; Mon, 23 May 2016 15:14:05 +0800 (CST) Received: from linux-4hy3.site (10.107.193.248) by szxeml432-hub.china.huawei.com (10.82.67.209) with Microsoft SMTP Server id 14.3.235.1; Mon, 23 May 2016 15:13:55 +0800 From: Wang Nan To: CC: , , Wang Nan , He Kuang , "Arnaldo Carvalho de Melo" , Jiri Olsa , Masami Hiramatsu , Namhyung Kim , "Zefan Li" Subject: [PATCH v3 03/11] perf record: Rename variable to make code clear Date: Mon, 23 May 2016 07:13:40 +0000 Message-ID: <1463987628-163563-4-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1463987628-163563-1-git-send-email-wangnan0@huawei.com> References: <1463987628-163563-1-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=0001.0A090205.5742ADBE.00C0, 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: 42ec920629032b7284a70df644fae8e8 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org record__mmap_read() write data from ring buffer into perf.data. 'head' is maintained by kernel, points to the last writtend record. 'old' is maintained by perf, points to the record read in previous round. record__mmap_read() saves data from 'old' to 'head' to perf.data. The names of these variables are not very intutive. In addition, when dealing with backward writing ring buffer, the md->prev pointer should point to 'head' instead of the last byte it got. Add start and end pointer to make code clear and set md->prev to 'head' instead of the moved 'old' pointer. This patch doesn't change behavior since: buf = &data[old & md->mask]; size = head - old; old += size; <--- Here, old == head Signed-off-by: Wang Nan Signed-off-by: He Kuang Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Zefan Li Cc: pi3orama@163.com --- tools/perf/builtin-record.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) -- 1.8.3.4 diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index f302cc9..73ce651 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -88,17 +88,18 @@ static int record__mmap_read(struct record *rec, int idx) struct perf_mmap *md = &rec->evlist->mmap[idx]; u64 head = perf_mmap__read_head(md); u64 old = md->prev; + u64 end = head, start = old; unsigned char *data = md->base + page_size; unsigned long size; void *buf; int rc = 0; - if (old == head) + if (start == end) return 0; rec->samples++; - size = head - old; + size = end - start; if (size > (unsigned long)(md->mask) + 1) { WARN_ONCE(1, "failed to keep up with mmap data. (warn only once)\n"); @@ -107,10 +108,10 @@ static int record__mmap_read(struct record *rec, int idx) return 0; } - if ((old & md->mask) + size != (head & md->mask)) { - buf = &data[old & md->mask]; - size = md->mask + 1 - (old & md->mask); - old += size; + if ((start & md->mask) + size != (end & md->mask)) { + buf = &data[start & md->mask]; + size = md->mask + 1 - (start & md->mask); + start += size; if (record__write(rec, buf, size) < 0) { rc = -1; @@ -118,16 +119,16 @@ static int record__mmap_read(struct record *rec, int idx) } } - buf = &data[old & md->mask]; - size = head - old; - old += size; + buf = &data[start & md->mask]; + size = end - start; + start += size; if (record__write(rec, buf, size) < 0) { rc = -1; goto out; } - md->prev = old; + md->prev = head; perf_evlist__mmap_consume(rec->evlist, idx); out: return rc;