From patchwork Fri May 6 00:29:40 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Arnaldo Carvalho de Melo X-Patchwork-Id: 67248 Delivered-To: patch@linaro.org Received: by 10.140.92.199 with SMTP id b65csp58958qge; Thu, 5 May 2016 17:32:24 -0700 (PDT) X-Received: by 10.66.236.167 with SMTP id uv7mr25215352pac.75.1462494744726; Thu, 05 May 2016 17:32:24 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id 12si13967300pft.105.2016.05.05.17.32.24; Thu, 05 May 2016 17:32:24 -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 S1758024AbcEFAcL (ORCPT + 29 others); Thu, 5 May 2016 20:32:11 -0400 Received: from merlin.infradead.org ([205.233.59.134]:55114 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757727AbcEFAaD (ORCPT ); Thu, 5 May 2016 20:30:03 -0400 Received: from [187.65.41.114] (helo=jouet.infradead.org) by merlin.infradead.org with esmtpsa (Exim 4.85_2 #1 (Red Hat Linux)) id 1ayTeR-0004lc-SW; Fri, 06 May 2016 00:29:52 +0000 Received: by jouet.infradead.org (Postfix, from userid 1000) id 43A55143815; Thu, 5 May 2016 21:29:47 -0300 (BRT) From: Arnaldo Carvalho de Melo To: Ingo Molnar Cc: linux-kernel@vger.kernel.org, Wang Nan , Peter Zijlstra , Zefan Li , pi3orama@163.com, Arnaldo Carvalho de Melo Subject: [PATCH 17/17] perf evlist: Rename variable in perf_mmap__read() Date: Thu, 5 May 2016 21:29:40 -0300 Message-Id: <1462494580-27164-18-git-send-email-acme@kernel.org> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1462494580-27164-1-git-send-email-acme@kernel.org> References: <1462494580-27164-1-git-send-email-acme@kernel.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by merlin.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Wang Nan In perf_mmap__read(), give better names to pointers. Original name 'old' and 'head' directly related to pointers in ring buffer control page. For backward ring buffer, the meaning of 'head' point is not 'the first byte of free space', but 'the first byte of the last record'. To reduce confusion, rename 'old' to 'start', 'head' to 'end'. 'start' -> 'end' is the direction the records should be read from. Change parameter order. Change 'overwrite' to 'check_messup'. When reading from 'head', no need to check messup for for backward ring buffer. Signed-off-by: Wang Nan Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1461723563-67451-3-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evlist.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) -- 2.5.5 diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 96c71916e367..17cd01421e7f 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -679,30 +679,31 @@ static struct perf_evsel *perf_evlist__event2evsel(struct perf_evlist *evlist, return NULL; } +/* When check_messup is true, 'end' must points to a good entry */ static union perf_event * -perf_mmap__read(struct perf_mmap *md, bool overwrite, u64 head, - u64 old, u64 *prev) +perf_mmap__read(struct perf_mmap *md, bool check_messup, u64 start, + u64 end, u64 *prev) { unsigned char *data = md->base + page_size; union perf_event *event = NULL; - int diff = head - old; + int diff = end - start; - if (overwrite) { + if (check_messup) { /* * If we're further behind than half the buffer, there's a chance * the writer will bite our tail and mess up the samples under us. * - * If we somehow ended up ahead of the head, we got messed up. + * If we somehow ended up ahead of the 'end', we got messed up. * - * In either case, truncate and restart at head. + * In either case, truncate and restart at 'end'. */ if (diff > md->mask / 2 || diff < 0) { fprintf(stderr, "WARNING: failed to keep up with mmap data.\n"); /* - * head points to a known good entry, start there. + * 'end' points to a known good entry, start there. */ - old = head; + start = end; diff = 0; } } @@ -710,7 +711,7 @@ perf_mmap__read(struct perf_mmap *md, bool overwrite, u64 head, if (diff >= (int)sizeof(event->header)) { size_t size; - event = (union perf_event *)&data[old & md->mask]; + event = (union perf_event *)&data[start & md->mask]; size = event->header.size; if (size < sizeof(event->header) || diff < (int)size) { @@ -722,8 +723,8 @@ perf_mmap__read(struct perf_mmap *md, bool overwrite, u64 head, * Event straddles the mmap boundary -- header should always * be inside due to u64 alignment of output. */ - if ((old & md->mask) + size != ((old + size) & md->mask)) { - unsigned int offset = old; + if ((start & md->mask) + size != ((start + size) & md->mask)) { + unsigned int offset = start; unsigned int len = min(sizeof(*event), size), cpy; void *dst = md->event_copy; @@ -738,12 +739,12 @@ perf_mmap__read(struct perf_mmap *md, bool overwrite, u64 head, event = (union perf_event *) md->event_copy; } - old += size; + start += size; } broken_event: if (prev) - *prev = old; + *prev = start; return event; } @@ -762,7 +763,7 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) head = perf_mmap__read_head(md); - return perf_mmap__read(md, evlist->overwrite, head, old, &md->prev); + return perf_mmap__read(md, evlist->overwrite, old, head, &md->prev); } static bool perf_mmap__empty(struct perf_mmap *md)