Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752736AbcD0CVK (ORCPT ); Tue, 26 Apr 2016 22:21:10 -0400 Received: from szxga03-in.huawei.com ([119.145.14.66]:35352 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752523AbcD0CVC (ORCPT ); Tue, 26 Apr 2016 22:21:02 -0400 From: Wang Nan To: CC: , Wang Nan , "Arnaldo Carvalho de Melo" , Peter Zijlstra , Zefan Li , Subject: [PATCH v2 3/4] perf tools: Support reading from backward ring buffer Date: Wed, 27 Apr 2016 02:19:22 +0000 Message-ID: <1461723563-67451-4-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1461723563-67451-1-git-send-email-wangnan0@huawei.com> References: <1461723563-67451-1-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=0001.0A0B0205.572021BC.0057,ss=1,re=0.000,recu=0.000,reip=0.000,cl=1,cld=1,fgs=0, ip=0.0.0.0, so=2013-05-26 15:14:31, dmn=2013-03-21 17:37:32 X-Mirapoint-Loop-Id: eefa2a3e49a1f27ccd27872f9bfb7b5c Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2625 Lines: 85 perf_evlist__mmap_read_backward() is introduced for reading backward ring buffer. Different from reading forward, before reading, caller needs to call perf_evlist__mmap_read_catchup() first. Backward ring buffer should be read from 'head' pointer, not '0'. perf_evlist__mmap_read_catchup() saves 'head' to 'md->prev', then make it remember the start position after each reading. Signed-off-by: Wang Nan Cc: Arnaldo Carvalho de Melo Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com --- tools/perf/util/evlist.c | 39 +++++++++++++++++++++++++++++++++++++++ tools/perf/util/evlist.h | 4 ++++ 2 files changed, 43 insertions(+) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 17cd014..2e0b7b0 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -766,6 +766,45 @@ union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx) return perf_mmap__read(md, evlist->overwrite, old, head, &md->prev); } +union perf_event * +perf_evlist__mmap_read_backward(struct perf_evlist *evlist, int idx) +{ + struct perf_mmap *md = &evlist->mmap[idx]; + u64 head, end; + u64 start = md->prev; + + /* + * Check if event was unmapped due to a POLLHUP/POLLERR. + */ + if (!atomic_read(&md->refcnt)) + return NULL; + + /* NOTE: head is negative in this case */ + head = perf_mmap__read_head(md); + + if (!head) + return NULL; + + end = head + md->mask + 1; + + if ((end - head) > -head) + end = 0; + + return perf_mmap__read(md, false, start, end, &md->prev); +} + +void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx) +{ + struct perf_mmap *md = &evlist->mmap[idx]; + u64 head; + + if (!atomic_read(&md->refcnt)) + return; + + head = perf_mmap__read_head(md); + md->prev = head; +} + static bool perf_mmap__empty(struct perf_mmap *md) { return perf_mmap__read_head(md) == md->prev && !md->auxtrace_mmap.base; diff --git a/tools/perf/util/evlist.h b/tools/perf/util/evlist.h index 208897a..85d1b59 100644 --- a/tools/perf/util/evlist.h +++ b/tools/perf/util/evlist.h @@ -129,6 +129,10 @@ struct perf_sample_id *perf_evlist__id2sid(struct perf_evlist *evlist, u64 id); union perf_event *perf_evlist__mmap_read(struct perf_evlist *evlist, int idx); +union perf_event *perf_evlist__mmap_read_backward(struct perf_evlist *evlist, + int idx); +void perf_evlist__mmap_read_catchup(struct perf_evlist *evlist, int idx); + void perf_evlist__mmap_consume(struct perf_evlist *evlist, int idx); int perf_evlist__open(struct perf_evlist *evlist); -- 1.8.3.4