lkml.org 
[lkml]   [2016]   [Feb]   [23]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [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@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

    \
     
     \ /
      Last update: 2016-02-23 19:01    [W:5.571 / U:0.056 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site