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Date: Wed, 24 Feb 2016 09:58:34 +0800
From: "Wangnan (F)" <wangnan0@...wei.com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>
CC: Alexei Starovoitov <ast@...nel.org>,
Arnaldo Carvalho de Melo <acme@...hat.com>,
Brendan Gregg <brendan.d.gregg@...il.com>,
Adrian Hunter <adrian.hunter@...el.com>,
Cody P Schafer <dev@...yps.com>,
"David S. Miller" <davem@...emloft.net>,
He Kuang <hekuang@...wei.com>,
Jérémie Galarneau
<jeremie.galarneau@...icios.com>, Jiri Olsa <jolsa@...nel.org>,
Kirill Smelkov <kirr@...edi.com>,
Li Zefan <lizefan@...wei.com>,
Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
Namhyung Kim <namhyung@...nel.org>,
Peter Zijlstra <peterz@...radead.org>, <pi3orama@....com>,
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 10/48] perf tools: Introduce bpf-output event
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 <uapi/linux/bpf.h>
>> 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;
>
> This is where I am hitting, with:
>
> [acme@...et linux]$ uname -r
> 4.5.0-rc4
>
> 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);
>
> And then:
>
> [root@...et bpf]# tail /sys/kernel/debug/tracing/trace
> perf-13040 [003] d... 12062.807729: : Error: failed to output: -95
> perf-13040 [003] d... 12062.807731: : Error: failed to output: -95
> perf-13040 [003] d... 12062.807732: : Error: failed to output: -95
> perf-13040 [003] d... 12062.807735: : Error: failed to output: -95
> perf-13040 [003] d... 12062.807737: : Error: failed to output: -95
> perf-13040 [003] d... 12062.807744: : Error: failed to output: -95
> gnome-terminal--3091 [001] d... 12062.807773: : Error: failed to output: -95
> gnome-terminal--3091 [001] d... 12062.807784: : Error: failed to output: -95
> gmain-2830 [002] d... 12062.811791: : Error: failed to output: -95
> gmain-2830 [002] d... 12062.811810: : Error: failed to output: -95
> [root@...et bpf]#
>
> Ideas? AFK for a while, will continue investigating.
I also noticed this output, but didn't digg into it because all events
I concerned is okay. I'll look into this today.
> This already was submitted to Ingo, BTW.
>
> I used, as in the changeset comment tests:
>
> perf record -a -e bpf-output/no-inherit,name=evt/ -e ./test_bpf_output.c/map:channel.event=evt/ ls /
>
> And perf script told me:
>
> [root@...et bpf]# perf script | tail
> perf 13040 [003] 12062.708337: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708339: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708340: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708341: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708343: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708344: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708346: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708347: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708348: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> perf 13040 [003] 12062.708350: evt: ffffffff81234eb1 sys_write (/lib/modules/4.5.0-rc4/build/vmlinux)
> [root@...et bpf]#
>
> Wonder where that /lib/modules/4.5.0-rc4/build/vmlinux came from...
>
> [root@...et bpf]# perf script | cut -d'(' -f2 | sort | uniq -c
> 1141 /lib/modules/4.5.0-rc4/build/vmlinux)
It's a standard directory for perf searching vmlinux. Isn't it?
tools/perf/util/symbol.c:
static const char * const vmlinux_paths_upd[] = {
"/boot/vmlinux-%s",
"/usr/lib/debug/boot/vmlinux-%s",
"/lib/modules/%s/build/vmlinux",
"/usr/lib/debug/lib/modules/%s/vmlinux",
"/usr/lib/debug/boot/vmlinux-%s.debug"
};
So what's your problem?
Thank you.
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