Messages in this thread | | | Date | Tue, 23 Feb 2016 14:45:39 -0300 | From | Arnaldo Carvalho de Melo <> | Subject | Re: [PATCH 10/48] perf tools: Introduce bpf-output event |
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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@jouet 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@jouet 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@jouet 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@jouet 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@jouet bpf]#
Wonder where that /lib/modules/4.5.0-rc4/build/vmlinux came from...
[root@jouet bpf]# perf script | cut -d'(' -f2 | sort | uniq -c 1141 /lib/modules/4.5.0-rc4/build/vmlinux)
- Arnaldo
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