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[209.132.180.67]) by mx.google.com with ESMTP id n74si3212331pfi.176.2016.05.10.08.16.45; Tue, 10 May 2016 08:16:45 -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 S1753198AbcEJPQb (ORCPT + 29 others); Tue, 10 May 2016 11:16:31 -0400 Received: from bombadil.infradead.org ([198.137.202.9]:39605 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752734AbcEJPQ1 (ORCPT ); Tue, 10 May 2016 11:16:27 -0400 Received: from [187.65.121.17] (helo=jouet.infradead.org) by bombadil.infradead.org with esmtpsa (Exim 4.80.1 #2 (Red Hat Linux)) id 1b09OV-0001x7-Kp; Tue, 10 May 2016 15:16:20 +0000 Received: by jouet.infradead.org (Postfix, from userid 1000) id 3DDBE14380B; Tue, 10 May 2016 12:16:16 -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 04/15] perf tools: Support reading from backward ring buffer Date: Tue, 10 May 2016 12:15:14 -0300 Message-Id: <1462893325-28646-5-git-send-email-acme@kernel.org> X-Mailer: git-send-email 2.5.5 In-Reply-To: <1462893325-28646-1-git-send-email-acme@kernel.org> References: <1462893325-28646-1-git-send-email-acme@kernel.org> X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.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 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(+) -- 2.5.5 diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 17cd01421e7f..c4bfe11479a0 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 208897a646ca..85d1b59802e8 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);