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Miller" , He Kuang , Jiri Olsa , Li Zefan , Masami Hiramatsu , Namhyung Kim , Peter Zijlstra , , Will Deacon , , Wang Nan Subject: [PATCH 52/54] perf record: Read from backward ring buffer Date: Mon, 25 Jan 2016 09:56:39 +0000 Message-ID: <1453715801-7732-53-git-send-email-wangnan0@huawei.com> X-Mailer: git-send-email 1.8.3.4 In-Reply-To: <1453715801-7732-1-git-send-email-wangnan0@huawei.com> References: <1453715801-7732-1-git-send-email-wangnan0@huawei.com> MIME-Version: 1.0 X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020203.56A5F1B1.0008, 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: fa681c18977f5a9ec4a65af04b0ae200 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Introduce rb_find_range() to find start and end position from a backward ring buffer. Signed-off-by: Wang Nan Signed-off-by: He Kuang Cc: Arnaldo Carvalho de Melo Cc: Jiri Olsa Cc: Masami Hiramatsu Cc: Namhyung Kim Cc: Zefan Li Cc: pi3orama@163.com --- tools/perf/builtin-record.c | 69 +++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 67 insertions(+), 2 deletions(-) -- 1.8.3.4 diff --git a/tools/perf/builtin-record.c b/tools/perf/builtin-record.c index 12147ef..1f03db0 100644 --- a/tools/perf/builtin-record.c +++ b/tools/perf/builtin-record.c @@ -86,6 +86,61 @@ static int process_synthesized_event(struct perf_tool *tool, return record__write(rec, event, event->header.size); } +static int +backward_rb_find_range(void *buf, int mask, u64 head, u64 *start, u64 *end) +{ + struct perf_event_header *pheader; + u64 evt_head = head; + int size = mask + 1; + + pr_debug2("backward_rb_find_range: buf=%p, head=%"PRIx64"\n", buf, head); + pheader = (struct perf_event_header *)(buf + (head & mask)); + *start = head; + while (true) { + if (evt_head - head >= (unsigned int)size) { + pr_debug("Finshed reading backward ring buffer: rewind\n"); + if (evt_head - head > (unsigned int)size) + evt_head -= pheader->size; + *end = evt_head; + return 0; + } + + pheader = (struct perf_event_header *)(buf + (evt_head & mask)); + + if (pheader->size == 0) { + pr_debug("Finshed reading backward ring buffer: get start\n"); + *end = evt_head; + return 0; + } + + evt_head += pheader->size; + pr_debug3("move evt_head: %"PRIx64"\n", evt_head); + } + WARN_ONCE(1, "Shouldn't get here\n"); + return -1; +} + +static int +rb_find_range(struct perf_evlist *evlist, int idx, + void *data, int mask, u64 head, u64 old, + u64 *start, u64 *end) +{ + int channel; + + channel = perf_evlist__idx_channel(evlist, idx); + if (!perf_evlist__channel_check(evlist, channel, RDONLY)) { + *start = old; + *end = head; + return 0; + } + + if (perf_evlist__channel_check(evlist, channel, BACKWARD)) + return backward_rb_find_range(data, mask, head, start, end); + + WARN_ONCE(1, "Unable to find start position from a read-only ring buffer\n"); + return -1; +} + static int record__mmap_read(struct record *rec, int idx) { struct perf_mmap *md = &rec->evlist->mmap[idx]; @@ -97,6 +152,10 @@ static int record__mmap_read(struct record *rec, int idx) void *buf; int rc = 0; + if (rb_find_range(rec->evlist, idx, data, md->mask, head, + old, &start, &end)) + return -1; + if (start == end) return 0; @@ -528,8 +587,14 @@ static bool record__mmap_should_read(struct record *rec, int idx) return false; if (perf_evlist__channel_idx(rec->evlist, &channel, &idx)) return false; - if (perf_evlist__channel_check(rec->evlist, channel, RDONLY)) - return false; + if (perf_evlist__channel_check(rec->evlist, channel, RDONLY)) { + if (rec->overwrite_evt_state != OVERWRITE_EVT_DATA_PENDING) + return false; + if (perf_evlist__channel_check(rec->evlist, channel, BACKWARD)) + return true; + else + return false; + } return true; }