Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753386AbdLDQxZ (ORCPT ); Mon, 4 Dec 2017 11:53:25 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:2203 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752255AbdLDQxN (ORCPT ); Mon, 4 Dec 2017 11:53:13 -0500 From: Wang Nan To: , , , , CC: , Wang Nan Subject: [PATCH v3 1/3] perf mmap: Fix perf backward recording Date: Mon, 4 Dec 2017 16:51:05 +0000 Message-ID: <20171204165107.95327-2-wangnan0@huawei.com> X-Mailer: git-send-email 2.10.1 In-Reply-To: <20171204165107.95327-1-wangnan0@huawei.com> References: <20171204165107.95327-1-wangnan0@huawei.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.107.193.248] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5765 Lines: 118 perf record backward recording doesn't work as we expected: it never overwrite when ring buffer full. Test: (Run a busy python printing task background like this: while True: print 123 send SIGUSR2 to perf to capture snapshot.) # ./perf record --overwrite -e raw_syscalls:sys_enter -e raw_syscalls:sys_exit --exclude-perf -a --switch-output [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101520743 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101521251 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101521692 ] ^C[ perf record: Woken up 1 times to write data ] [ perf record: Dump perf.data.2017110101521936 ] [ perf record: Captured and wrote 0.826 MB perf.data. ] # ./perf script -i ./perf.data.2017110101520743 | head -n3 perf 2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0) perf 2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0) python 2545 [000] 12449.310800: raw_syscalls:sys_exit: NR 1 = 4 # ./perf script -i ./perf.data.2017110101521251 | head -n3 perf 2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0) perf 2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0) python 2545 [000] 12449.310800: raw_syscalls:sys_exit: NR 1 = 4 # ./perf script -i ./perf.data.2017110101521692 | head -n3 perf 2717 [000] 12449.310785: raw_syscalls:sys_enter: NR 16 (5, 2400, 0, 59, 100, 0) perf 2717 [000] 12449.310790: raw_syscalls:sys_enter: NR 7 (4112340, 2, ffffffff, 3df, 100, 0) python 2545 [000] 12449.310800: raw_syscalls:sys_exit: NR 1 = 4 Timestamps are never change, but my background task is a dead loop, can easily overwhelme the ring buffer. This patch fix it by force unsetting PROT_WRITE for backward ring buffer, so all backward ring buffer become overwrite ring buffer. Test result: # ./perf record --overwrite -e raw_syscalls:sys_enter -e raw_syscalls:sys_exit --exclude-perf -a --switch-output [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101285323 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101290053 ] [ perf record: dump data: Woken up 1 times ] [ perf record: Dump perf.data.2017110101290446 ] ^C[ perf record: Woken up 1 times to write data ] [ perf record: Dump perf.data.2017110101290837 ] [ perf record: Captured and wrote 0.826 MB perf.data. ] # ./perf script -i ./perf.data.2017110101285323 | head -n3 python 2545 [000] 11064.268083: raw_syscalls:sys_exit: NR 1 = 4 python 2545 [000] 11064.268084: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0) python 2545 [000] 11064.268086: raw_syscalls:sys_exit: NR 1 = 4 # ./perf script -i ./perf.data.2017110101290 | head -n3 failed to open ./perf.data.2017110101290: No such file or directory # ./perf script -i ./perf.data.2017110101290053 | head -n3 python 2545 [000] 11071.564062: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0) python 2545 [000] 11071.564064: raw_syscalls:sys_exit: NR 1 = 4 python 2545 [000] 11071.564066: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0) # ./perf script -i ./perf.data.2017110101290 | head -n3 perf.data.2017110101290053 perf.data.2017110101290446 perf.data.2017110101290837 # ./perf script -i ./perf.data.2017110101290446 | head -n3 sshd 1321 [000] 11075.499473: raw_syscalls:sys_exit: NR 14 = 0 sshd 1321 [000] 11075.499474: raw_syscalls:sys_enter: NR 14 (2, 7ffe98899490, 0, 8, 0, 3000) sshd 1321 [000] 11075.499474: raw_syscalls:sys_exit: NR 14 = 0 # ./perf script -i ./perf.data.2017110101290837 | head -n3 python 2545 [000] 11079.280844: raw_syscalls:sys_exit: NR 1 = 4 python 2545 [000] 11079.280847: raw_syscalls:sys_enter: NR 1 (1, 12cc330, 4, 7fc237280370, 7fc2373d0700, 2c7b0) python 2545 [000] 11079.280850: raw_syscalls:sys_exit: NR 1 = 4 Signed-off-by: Wang Nan --- tools/perf/util/evlist.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c index 68c1f95..b1cea71 100644 --- a/tools/perf/util/evlist.c +++ b/tools/perf/util/evlist.c @@ -812,6 +812,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx, int fd; int cpu; + mp->prot = PROT_READ | PROT_WRITE; if (evsel->attr.write_backward) { output = _output_backward; maps = evlist->backward_mmap; @@ -824,6 +825,7 @@ static int perf_evlist__mmap_per_evsel(struct perf_evlist *evlist, int idx, if (evlist->bkw_mmap_state == BKW_MMAP_NOTREADY) perf_evlist__toggle_bkw_mmap(evlist, BKW_MMAP_RUNNING); } + mp->prot &= ~PROT_WRITE; } if (evsel->system_wide && thread) @@ -1058,9 +1060,12 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages, struct perf_evsel *evsel; const struct cpu_map *cpus = evlist->cpus; const struct thread_map *threads = evlist->threads; - struct mmap_params mp = { - .prot = PROT_READ | PROT_WRITE, - }; + /* + * Delay setting mp.prot: set it before calling perf_mmap__mmap. + * Its value is decided by evsel's write_backward. + * So &mp should not be passed through const pointer. + */ + struct mmap_params mp; if (!evlist->mmap) evlist->mmap = perf_evlist__alloc_mmap(evlist); -- 2.10.1