From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753051AbcEJUcY (ORCPT ); Tue, 10 May 2016 16:32:24 -0400 Received: from terminus.zytor.com ([198.137.202.10]:58186 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752192AbcEJUcW (ORCPT ); Tue, 10 May 2016 16:32:22 -0400 Date: Tue, 10 May 2016 13:31:46 -0700 From: tip-bot for Wang Nan Message-ID: Cc: tglx@linutronix.de, lizefan@huawei.com, acme@redhat.com, mingo@kernel.org, wangnan0@huawei.com, hpa@zytor.com, linux-kernel@vger.kernel.org, peterz@infradead.org Reply-To: hpa@zytor.com, wangnan0@huawei.com, mingo@kernel.org, peterz@infradead.org, linux-kernel@vger.kernel.org, acme@redhat.com, lizefan@huawei.com, tglx@linutronix.de In-Reply-To: <1462758471-89706-2-git-send-email-wangnan0@huawei.com> References: <1462758471-89706-2-git-send-email-wangnan0@huawei.com> To: linux-tip-commits@vger.kernel.org Subject: [tip:perf/core] perf tools: Support reading from backward ring buffer Git-Commit-ID: e24c7520ea9c3e5bb51592c2134aafbf75a3f88a 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: e24c7520ea9c3e5bb51592c2134aafbf75a3f88a Gitweb: http://git.kernel.org/tip/e24c7520ea9c3e5bb51592c2134aafbf75a3f88a Author: Wang Nan AuthorDate: Mon, 9 May 2016 01:47:50 +0000 Committer: Arnaldo Carvalho de Melo CommitDate: Mon, 9 May 2016 17:20:53 -0300 perf tools: Support reading from backward ring buffer perf_evlist__mmap_read_backward() is introduced for reading backward ring buffer. Since direction for reading such ring buffer is different from the direction kernel writing to it, and since user need to fetch most recent record from it, a perf_evlist__mmap_read_catchup() is introduced to move the reading pointer to the end of the buffer. Signed-off-by: Wang Nan Cc: Peter Zijlstra Cc: Zefan Li Cc: pi3orama@163.com Link: http://lkml.kernel.org/r/1462758471-89706-2-git-send-email-wangnan0@huawei.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evlist.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++ tools/perf/util/evlist.h | 4 ++++ 2 files changed, 54 insertions(+) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 17cd014..c4bfe11 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -766,6 +766,56 @@ 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; + + head = perf_mmap__read_head(md); + if (!head) + return NULL; + + /* + * 'head' pointer starts from 0. Kernel minus sizeof(record) form + * it each time when kernel writes to it, so in fact 'head' is + * negative. 'end' pointer is made manually by adding the size of + * the ring buffer to 'head' pointer, means the validate data can + * read is the whole ring buffer. If 'end' is positive, the ring + * buffer has not fully filled, so we must adjust 'end' to 0. + * + * However, since both 'head' and 'end' is unsigned, we can't + * simply compare 'end' against 0. Here we compare '-head' and + * the size of the ring buffer, where -head is the number of bytes + * kernel write to the ring buffer. + */ + if (-head < (u64)(md->mask + 1)) + end = 0; + else + end = head + md->mask + 1; + + 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);