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Date: Tue, 23 Feb 2016 14:45:39 -0300
From: Arnaldo Carvalho de Melo <acme@...nel.org>
To: Wang Nan <wangnan0@...wei.com>
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
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.
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)
- Arnaldo
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