Messages in this thread | | | From | Yang Shi <> | Date | Wed, 8 Mar 2023 11:56:38 -0800 | Subject | Re: [BUG] perf: No samples found when using kcore + coresight |
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On Tue, Mar 7, 2023 at 11:45 AM Yang Shi <shy828301@gmail.com> wrote: > > Hi James, > > Thanks for the prompt response. Please see the inline replies. > > On Tue, Mar 7, 2023 at 2:32 AM James Clark <james.clark@arm.com> wrote: > > > > > > > > On 06/03/2023 21:13, Yang Shi wrote: > > > Hi, > > > > > > I'm seeking some help regarding perf record --kcore + coresight. When > > > I tracing with perf record --kcore -e cs_etm ... , perf report shows > > > "The perf.data/data data has no samples!". > > > > > > I tried other combinations: > > > 1. perf record --kcore (w/o using coresight): works > > > 2. perf record -e cs_etm ... : works > > > 3. Manually copy kcore with perf buildid-cache, then run perf record > > > -e cs_etm... : works > > > > > > So just "perf record --kcore -e cs_etm ..." doesn't work. > > > > > > I'm using v6.2 kernel and the perf is built from the same kernel > > > source with OpenCSD 1.4. Also attached the sample file generated by > > > perf. > > > > > > Any suggestion is appreciated. > > > > > > Thanks, > > > Yang > > > > Hi Yang, > > > > I don't see any issue with this command and I still get samples: > > > > perf record -e cs_etm// --kcore -- true > > This command works for me. But the below command doesn't work: > > perf record --kcore -e cs_etm/@tmc_etf63/k --per-thread -- taskset > --cpu-list 1 uname > > > > > You might want to try running both record and report in verbose and > > stdio mode (-vvv --stdio) to see if you see any warnings. > > > > I can't think of any way --kcore would cause an issue because all it > > does is save kcore into the .debug cache rather than affecting the > > actual perf.data file. > > Yes, this is what I thought. But digging into the code seems it may > add a new dummy event. Please see the below data header dump. > > > > > Are you running perf report in the same place the recording was made? Or > > on another system? > > Yes. > > I did some further investigation. The below is the dump for both good > and bad data files. > > Good (copy kcore manually): > # captured on : Tue Mar 7 11:19:14 2023 > # header version : 1 > # data offset : 1576 > # data size : 26736 > # feat offset : 28312 > # hostname : fedora > # os release : 6.2.0-coresight+ > # perf version : 6.2.g3424af22c4fc > # arch : aarch64 > # nrcpus online : 128 > # nrcpus avail : 128 > # cpuid : 0x00000000c00fac30 > # total memory : 2108862504 kB > # cmdline : /root/bin/perf record -e cs_etm/@tmc_etf63/k --kcore > --per-thread -- taskset --cpu-list 1 true > # event : name = cs_etm/@tmc_etf63/k, , id = { 2248 }, type = 9, size > = 128, { sample_period, sample_freq } = 1, sample_type = > IP|TID|IDENTIFIER, read_format = ID|LO > ST, disabled = 1, exclude_user = 1, exclude_hv = 1, enable_on_exec = > 1, sample_id_all = 1, { bp_len, config2 } = 0x12792918 > # event : name = dummy:u, , id = { 2249 }, type = 1, size = 128, > config = 0x9, { sample_period, sample_freq } = 1, sample_type = > IP|TID|IDENTIFIER, read_format = ID| > LOST, disabled = 1, exclude_kernel = 1, exclude_hv = 1, mmap = 1, comm > = 1, enable_on_exec = 1, task = 1, sample_id_all = 1, exclude_guest = > 1, mmap2 = 1, comm_exec > = 1, context_switch = 1, bpf_event = 1 > # event : name = dummy:u, , id = { 2250, 2251, 2252, 2253, 2254, 2255, > 2256, 2257, 2258, 2259, 2260, 2261, 2262, 2263, 2264, 2265, 2266, > 2267, 2268, 2269, 2270, 2271 > , 2272, 2273, 2274, 2275, 2276, 2277, 2278, 2279, 2280, 2281, 2282, > 2283, 2284, 2285, 2286, 2287, 2288, 2289, 2290, 2291, 2292, 2293, > 2294, 2295, 2296, 2297, 2298, 2 > 299, 2300, 2301, 2302, 2303, 2304, 2305, 2306, 2307, 2308, 2309, 2310, > 2311, 2312, 2313, 2314, 2315, 2316, 2317, 2318, 2319, 2320, 2321, > 2322, 2323, 2324, 2325, 2326 > , 2327, 2328, 2329, 2330, 2331, 2332, 2333, 2334, 2335, 2336, 2337, > 2338, 2339, 2340, 2341, 2342, 2343, 2344, 2345, 2346, 2347, 2348, > 2349, 2350, 2351, 2352, 2353, 2 > 354, 2355, 2356, 2357, 2358, 2359, 2360, 2361, 2362, 2363, 2364, 2365, > 2366, 2367, 2368, 2369, 2370, 2371, 2372, 2373, 2374, 2375, 2376, 2377 > }, type = 1, size = 128 > , config = 0x9, { sample_period, sample_freq } = 1, sample_type = > IP|TID|TIME|IDENTIFIER, read_format = ID|LOST, exclude_kernel = 1, > exclude_hv = 1, sample_id_all = > 1, exclude_guest = 1, ksymbol = 1, text_poke = 1 > # CPU_TOPOLOGY info available, use -I to display > # NUMA_TOPOLOGY info available, use -I to display > # pmu mappings: armv8_pmuv3_0 = 8, software = 1, arm_cmn_0 = 10, > uprobe = 7, cs_etm = 9, breakpoint = 5, tracepoint = 2, arm_cmn_1 = > 11, kprobe = 6 > # contains AUX area data (e.g. instruction trace) > # CACHE info available, use -I to display > # time of first sample : 18446744073.709551 > # time of last sample : 18446744073.709551 > # sample duration : 0.000 ms > # MEM_TOPOLOGY info available, use -I to display > # armv8_pmuv3_0 pmu capabilities: slots=0x00000004, > bus_slots=0x00000000, bus_width=0x00000000 > # missing features: (null) CPUDESC BRANCH_STACK GROUP_DESC STAT > CLOCKID DIR_FORMAT COMPRESSED CPU_PMU_CAPS CLOCK_DATA HYBRID_TOPOLOGY > > Bad: > # captured on : Tue Mar 7 11:19:14 2023 > # header version : 1 > # data offset : 1576 > # data size : 26736 > # feat offset : 28312 > # hostname : fedora > # os release : 6.2.0-coresight+ > # perf version : 6.2.g3424af22c4fc > # arch : aarch64 > # nrcpus online : 128 > # nrcpus avail : 128 > # cpuid : 0x00000000c00fac30 > # total memory : 2108862504 kB > # cmdline : /root/bin/perf record -e cs_etm/@tmc_etf63/k --kcore > --per-thread -- taskset --cpu-list 1 true > # event : name = cs_etm/@tmc_etf63/k, , id = { 2248 }, type = 9, size > = 128, { sample_period, sample_freq } = 1, sample_type = > IP|TID|IDENTIFIER, read_format = ID|LO > ST, disabled = 1, exclude_user = 1, exclude_hv = 1, enable_on_exec = > 1, sample_id_all = 1, { bp_len, config2 } = 0x12792918 > # event : name = dummy:u, , id = { 2249 }, type = 1, size = 128, > config = 0x9, { sample_period, sample_freq } = 1, sample_type = > IP|TID|IDENTIFIER, read_format = ID| > LOST, disabled = 1, exclude_kernel = 1, exclude_hv = 1, mmap = 1, comm > = 1, enable_on_exec = 1, task = 1, sample_id_all = 1, exclude_guest = > 1, mmap2 = 1, comm_exec > = 1, context_switch = 1, bpf_event = 1 > # event : name = dummy:u, , id = { 2250, 2251, 2252, 2253, 2254, 2255, > 2256, 2257, 2258, 2259, 2260, 2261, 2262, 2263, 2264, 2265, 2266, > 2267, 2268, 2269, 2270, 2271 > , 2272, 2273, 2274, 2275, 2276, 2277, 2278, 2279, 2280, 2281, 2282, > 2283, 2284, 2285, 2286, 2287, 2288, 2289, 2290, 2291, 2292, 2293, > 2294, 2295, 2296, 2297, 2298, 2 > 299, 2300, 2301, 2302, 2303, 2304, 2305, 2306, 2307, 2308, 2309, 2310, > 2311, 2312, 2313, 2314, 2315, 2316, 2317, 2318, 2319, 2320, 2321, > 2322, 2323, 2324, 2325, 2326 > , 2327, 2328, 2329, 2330, 2331, 2332, 2333, 2334, 2335, 2336, 2337, > 2338, 2339, 2340, 2341, 2342, 2343, 2344, 2345, 2346, 2347, 2348, > 2349, 2350, 2351, 2352, 2353, 2 > 354, 2355, 2356, 2357, 2358, 2359, 2360, 2361, 2362, 2363, 2364, 2365, > 2366, 2367, 2368, 2369, 2370, 2371, 2372, 2373, 2374, 2375, 2376, 2377 > }, type = 1, size = 128 > , config = 0x9, { sample_period, sample_freq } = 1, sample_type = > IP|TID|TIME|IDENTIFIER, read_format = ID|LOST, exclude_kernel = 1, > exclude_hv = 1, sample_id_all = > 1, exclude_guest = 1, ksymbol = 1, text_poke = 1 > # CPU_TOPOLOGY info available, use -I to display > # NUMA_TOPOLOGY info available, use -I to display > # pmu mappings: armv8_pmuv3_0 = 8, software = 1, arm_cmn_0 = 10, > uprobe = 7, cs_etm = 9, breakpoint = 5, tracepoint = 2, arm_cmn_1 = > 11, kprobe = 6 > # contains AUX area data (e.g. instruction trace) > # CACHE info available, use -I to display > # time of first sample : 18446744073.709551 > # time of last sample : 18446744073.709551 > # sample duration : 0.000 ms > # MEM_TOPOLOGY info available, use -I to display > # armv8_pmuv3_0 pmu capabilities: slots=0x00000004, > bus_slots=0x00000000, bus_width=0x00000000 > # missing features: (null) CPUDESC BRANCH_STACK GROUP_DESC STAT > CLOCKID DIR_FORMAT COMPRESSED CPU_PMU_CAPS CLOCK_DATA HYBRID_TOPOLOGY > > > Dumping raw events could show the events from the bad data file. But > it has zero samples after event collapse. > > The only difference is --kcore inserted a new text_poke dummy event. > It seems coresight also inserted a dummy event with my command but > your command didn't. So it seems like the two dummy events confused > event collapse. > > The text_poke dummy event is added by commit > f42c0ce573df79d1b8bd169008c994dcdd43585a ("perf record: Always get > text_poke events with --kcore option"). If I reverted this commit, > then it works. But I'm not sure whether this is the right fix or real > root cause or not. Or coresight shouldn't insert its own dummy event?
It seems like coresight needs to insert the dummy event if full_auxtrace is on IIUC. So it sounds like event collapse can't handle such a case? I also tried v5.19 (before "perf record: Always get text_poke events with --kcore option", which was merged in v6.0), it works. So it seems like a regression.
> > > > > James
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