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test_perf_event: large value for CPU cycles
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riya
So the following change fixes the problem:
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diff --git a/src/cc/export/helpers.h b/src/cc/export/helpers.h index a5afa44..c4fbac6 100644 --- a/src/cc/export/helpers.h +++ b/src/cc/export/helpers.h @@ -166,7 +166,7 @@ static int (*bpf_skb_get_tunnel_key)(void *ctx, void *to, u32 size, u64 flags) = (void *) BPF_FUNC_skb_get_tunnel_key; static int (*bpf_skb_set_tunnel_key)(void *ctx, void *from, u32 size, u64 flags) = (void *) BPF_FUNC_skb_set_tunnel_key; -static int (*bpf_perf_event_read)(void *map, u32 index) = +static u64 (*bpf_perf_event_read)(void *map, u32 index) = (void *) BPF_FUNC_perf_event_read; static int (*bpf_redirect)(int ifindex, u32 flags) = (void *) BPF_FUNC_redirect; On Tue, Aug 30, 2016 at 12:22 AM, riya khanna <riyakhanna1983@...> wrote:
Looks like its due to sign extension when copied from |
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riya
Looks like its due to sign extension when copied from
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perf_event_read_local to BPF userspace. On Mon, Aug 29, 2016 at 5:12 PM, riya khanna <riyakhanna1983@...> wrote:
Hi, |
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riya
Hi,
I'm running tests/python/test_perf_event.py. I changed the following to print out 'cpu cycles' value and increased the number of times 'getuid()' syscall is executed: diff --git a/tests/python/test_perf_event.py b/tests/python/test_perf_event.py index 224faff..bd9e268 100755 --- a/tests/python/test_perf_event.py +++ b/tests/python/test_perf_event.py @@ -18,12 +18,14 @@ BPF_HISTOGRAM(dist); int kprobe__sys_getuid(void *ctx) { u32 cpu = bpf_get_smp_processor_id(); u64 val = cnt1.perf_read(cpu); + bpf_trace_printk("entry: cycls: %llu\\n", val); prev.update(&cpu, &val); return 0; } int kretprobe__sys_getuid(void *ctx) { u32 cpu = bpf_get_smp_processor_id(); u64 val = cnt1.perf_read(cpu); + bpf_trace_printk("exit: cycls: %llu\\n", val); u64 *prevp = prev.lookup(&cpu); if (prevp) dist.increment(bpf_log2l(val - *prevp)); @@ -39,7 +41,7 @@ int kretprobe__sys_getuid(void *ctx) { if ctypes.get_errno() == 2: raise self.skipTest("hardware events unsupported") raise - for i in range(0, 100): + for i in range(0, 10000000): os.getuid() b["dist"].print_log2_hist() With this change, I sometimes see very high value for 'CPU cycles' counter (see output below) Is this expected? Please let me know. Thanks! I've already disabled NMI by doing sudo sh -c "echo 0 > /proc/sys/kernel/nmi_watchdog" sudo-8580 [006] d... 10746.773075: : entry: cycls: 1874922986 sudo-8580 [006] d... 10746.773092: : exit: cycls: 1874922986 sudo-8580 [001] d... 10746.778428: : entry: cycls: 144504920 sudo-8580 [001] d... 10746.778459: : exit: cycls: 144504920 sudo-8580 [001] d... 10746.778588: : entry: cycls: 144597669 sudo-8580 [001] d... 10746.778598: : exit: cycls: 144597669 sh-8581 [007] d... 10746.779968: : entry: cycls: 18446744071909310443 sh-8581 [007] d... 10746.779981: : exit: cycls: 18446744071909310443 sudo-8580 [000] d... 10746.780445: : entry: cycls: 18446744072592498664 sudo-8580 [000] d... 10746.780459: : exit: cycls: 18446744072592498664 sshd-8679 [001] d... 10749.599000: : entry: cycls: 173580086 sshd-8679 [001] d... 10749.599017: : exit: cycls: 173580086 sshd-8679 [001] d... 10749.641906: : entry: cycls: 230568964 sshd-8679 [001] d... 10749.641916: : exit: cycls: 230568964 sshd-8679 [001] d... 10749.641921: : entry: cycls: 230571582 sshd-8679 [001] d... 10749.641922: : exit: cycls: 230571582 sshd-8679 [001] d... 10749.641926: : entry: cycls: 230573602 sshd-8679 [001] d... 10749.641927: : exit: cycls: 230573602 sshd-8679 [001] d... 10749.641930: : entry: cycls: 230575185 sshd-8679 [001] d... 10749.641931: : exit: cycls: 230575185 sshd-8679 [001] d... 10749.642585: : entry: cycls: 231016394 sshd-8679 [001] d... 10749.642594: : exit: cycls: 231016394 sshd-8679 [001] d... 10749.643903: : entry: cycls: 232919009 sshd-8679 [001] d... 10749.643911: : exit: cycls: 232919009 sshd-8679 [001] d... 10749.644015: : entry: cycls: 233038255 sshd-8679 [001] d... 10749.644022: : exit: cycls: 233038255 sshd-8679 [001] d... 10749.644660: : entry: cycls: 233943332 sshd-8679 [001] d... 10749.644667: : exit: cycls: 233943332 sshd-8680 [007] d... 10749.645712: : entry: cycls: 18446744071924982598 sshd-8680 [007] d... 10749.645726: : exit: cycls: 18446744071924982598 sshd-8680 [007] d... 10749.645759: : entry: cycls: 18446744071924986843 sshd-8680 [007] d... 10749.645761: : exit: cycls: 18446744071924986843 |
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