From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752598AbcBXCHw (ORCPT ); Tue, 23 Feb 2016 21:07:52 -0500 Received: from szxga03-in.huawei.com ([119.145.14.66]:13761 "EHLO szxga03-in.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751236AbcBXCHu (ORCPT ); Tue, 23 Feb 2016 21:07:50 -0500 Subject: Re: [PATCH 10/48] perf tools: Introduce bpf-output event To: Arnaldo Carvalho de Melo References: <1456132275-98875-1-git-send-email-wangnan0@huawei.com> <1456132275-98875-11-git-send-email-wangnan0@huawei.com> <20160223174539.GG15284@kernel.org> <56CD0E4A.9080804@huawei.com> CC: Alexei Starovoitov , Arnaldo Carvalho de Melo , Brendan Gregg , Adrian Hunter , Cody P Schafer , "David S. Miller" , He Kuang , =?UTF-8?Q?J=c3=a9r=c3=a9mie_Galarneau?= , Jiri Olsa , Kirill Smelkov , Li Zefan , Masami Hiramatsu , Namhyung Kim , Peter Zijlstra , , From: "Wangnan (F)" Message-ID: <56CD0FC4.3070305@huawei.com> Date: Wed, 24 Feb 2016 10:04:52 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.5.0 MIME-Version: 1.0 In-Reply-To: <56CD0E4A.9080804@huawei.com> Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 7bit X-Originating-IP: [10.111.66.109] X-CFilter-Loop: Reflected X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A020202.56CD1029.0050,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: 1c838656e0eb1466008408c0246019d9 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2016/2/24 9:58, Wangnan (F) wrote: > > > On 2016/2/24 1:45, Arnaldo Carvalho de Melo wrote: >> Em Mon, Feb 22, 2016 at 09:10:37AM +0000, Wang Nan escreveu: >>> Commit a43eec304259a6c637f4014a6d4767159b6a3aa3 (bpf: introduce >>> bpf_perf_event_output() helper) add a helper to enable BPF program >>> output data to perf ring buffer through a new type of perf event >>> PERF_COUNT_SW_BPF_OUTPUT. This patch enable perf to create perf >>> event of that type. Now perf user can use following cmdline to >>> receive output data from BPF programs: >>> >>> # ./perf record -a -e bpf-output/no-inherit,name=evt/ \ >>> -e ./test_bpf_output.c/map:channel.event=evt/ ls / >>> # ./perf script >>> perf 1560 [004] 347747.086295: >>> evt: ffffffff811fd201 sys_write ... >>> perf 1560 [004] 347747.086300: >>> evt: ffffffff811fd201 sys_write ... >>> perf 1560 [004] 347747.086315: >>> evt: ffffffff811fd201 sys_write ... >>> ... >>> >>> Test result: >>> # cat ./test_bpf_output.c >>> /************************ BEGIN **************************/ >>> #include >>> struct bpf_map_def { >>> unsigned int type; >>> unsigned int key_size; >>> unsigned int value_size; >>> unsigned int max_entries; >>> }; >>> >>> #define SEC(NAME) __attribute__((section(NAME), used)) >>> static u64 (*ktime_get_ns)(void) = >>> (void *)BPF_FUNC_ktime_get_ns; >>> static int (*trace_printk)(const char *fmt, int fmt_size, ...) = >>> (void *)BPF_FUNC_trace_printk; >>> static int (*get_smp_processor_id)(void) = >>> (void *)BPF_FUNC_get_smp_processor_id; >>> static int (*perf_event_output)(void *, struct bpf_map_def *, int, >>> void *, unsigned long) = >>> (void *)BPF_FUNC_perf_event_output; >>> >>> struct bpf_map_def SEC("maps") channel = { >>> .type = BPF_MAP_TYPE_PERF_EVENT_ARRAY, >>> .key_size = sizeof(int), >>> .value_size = sizeof(u32), >>> .max_entries = __NR_CPUS__, >>> }; >>> >>> SEC("func_write=sys_write") >>> int func_write(void *ctx) >>> { >>> struct { >>> u64 ktime; >>> int cpuid; >>> } __attribute__((packed)) output_data; >>> char error_data[] = "Error: failed to output: %d\n"; >>> >>> output_data.cpuid = get_smp_processor_id(); >>> output_data.ktime = ktime_get_ns(); >>> int err = perf_event_output(ctx, &channel, >>> get_smp_processor_id(), >>> &output_data, sizeof(output_data)); >>> if (err) >>> trace_printk(error_data, sizeof(error_data), err); >>> return 0; >>> } >>> char _license[] SEC("license") = "GPL"; >>> int _version SEC("version") = LINUX_VERSION_CODE; >>> /************************ END ***************************/ >>> >>> # ./perf record -a -e bpf-output/no-inherit,name=evt/ \ >>> -e ./test_bpf_output.c/map:channel.event=evt/ ls / >>> # ./perf script | grep ls >>> ls 2242 [003] 347851.557563: evt: ffffffff811fd201 >>> sys_write ... >>> ls 2242 [003] 347851.557571: evt: ffffffff811fd201 >>> sys_write ... >> So, there is something strange here: >> >> if (unlikely(event->oncpu != smp_processor_id())) >> return -EOPNOTSUPP; >> > All failures have 'event->oncpu == -1' here. I guess we should suppress warning in this case. But why event->oncpu becomes -1? Thank you.