From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754260AbcEXFtL (ORCPT ); Tue, 24 May 2016 01:49:11 -0400 Received: from terminus.zytor.com ([198.137.202.10]:51996 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753260AbcEXFtJ (ORCPT ); Tue, 24 May 2016 01:49:09 -0400 Date: Mon, 23 May 2016 22:48:54 -0700 From: tip-bot for Wang Nan Message-ID: Cc: masami.hiramatsu.pt@hitachi.com, tglx@linutronix.de, wangnan0@huawei.com, hpa@zytor.com, namhyung@kernel.org, mingo@kernel.org, acme@redhat.com, hekuang@huawei.com, linux-kernel@vger.kernel.org, lizefan@huawei.com, jolsa@kernel.org Reply-To: mingo@kernel.org, acme@redhat.com, hekuang@huawei.com, linux-kernel@vger.kernel.org, lizefan@huawei.com, jolsa@kernel.org, tglx@linutronix.de, masami.hiramatsu.pt@hitachi.com, wangnan0@huawei.com, hpa@zytor.com, namhyung@kernel.org In-Reply-To: <1463987628-163563-4-git-send-email-wangnan0@huawei.com> References: <1463987628-163563-4-git-send-email-wangnan0@huawei.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/urgent] perf record: Rename variable to make code clear Git-Commit-ID: 09fa4f401296f555afb6f2f4282717644d94722e 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 Commit-ID: 09fa4f401296f555afb6f2f4282717644d94722e Gitweb: http://git.kernel.org/tip/09fa4f401296f555afb6f2f4282717644d94722e Author: Wang Nan AuthorDate: Mon, 23 May 2016 07:13:40 +0000 Committer: Arnaldo Carvalho de Melo CommitDate: Mon, 23 May 2016 18:22:47 -0300 perf record: Rename variable to make code clear record__mmap_read() writes data from ring buffer into perf.data. 'head' is maintained by the kernel, points to the last written 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 Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1463987628-163563-4-git-send-email-wangnan0@huawei.com Signed-off-by: He Kuang Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/builtin-record.c | 21 +++++++++++---------- 1 file changed, 11 insertions(+), 10 deletions(-) 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;