From aa97293ff129f504e7c8589e56007ecfe3e3e835 Mon Sep 17 00:00:00 2001 From: Igor Lubashev Date: Mon, 26 Aug 2019 21:39:14 -0400 Subject: [PATCH] perf evsel: Kernel profiling is disallowed only when perf_event_paranoid > 1 Perf was too restrictive about sysctl kernel.perf_event_paranoid. The kernel only disallows profiling when perf_event_paranoid > 1. Make perf do the same. Committer testing: For a non-root user: $ id uid=1000(acme) gid=1000(acme) groups=1000(acme),10(wheel) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023 $ Before: We were restricting it to just userspace (:u suffix) even for a workload started by the user: $ perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.001 MB perf.data (8 samples) ] $ perf evlist cycles:u $ perf evlist -v cycles:u: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, read_format: ID, disabled: 1, inherit: 1, exclude_kernel: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1 $ perf report --stdio # To display the perf.data header info, please use --header/--header-only options. # # Total Lost Samples: 0 # # Samples: 8 of event 'cycles:u' # Event count (approx.): 1040396 # # Overhead Command Shared Object Symbol # ........ ....... ................ ...................... # 68.36% sleep libc-2.29.so [.] _dl_addr 27.33% sleep ld-2.29.so [.] dl_main 3.80% sleep ld-2.29.so [.] _dl_setup_hash # # (Tip: Order by the overhead of source file name and line number: perf report -s srcline) # $ $ After: When the kernel allows profiling the kernel in that scenario: $ perf record sleep 1 [ perf record: Woken up 1 times to write data ] [ perf record: Captured and wrote 0.023 MB perf.data (11 samples) ] $ perf evlist cycles $ perf evlist -v cycles: size: 112, { sample_period, sample_freq }: 4000, sample_type: IP|TID|TIME|PERIOD, read_format: ID, disabled: 1, inherit: 1, mmap: 1, comm: 1, freq: 1, enable_on_exec: 1, task: 1, precise_ip: 3, sample_id_all: 1, exclude_guest: 1, mmap2: 1, comm_exec: 1, ksymbol: 1, bpf_event: 1 $ $ perf report --stdio # To display the perf.data header info, please use --header/--header-only options. # # Total Lost Samples: 0 # # Samples: 11 of event 'cycles' # Event count (approx.): 1601964 # # Overhead Command Shared Object Symbol # ........ ....... ................ .......................... # 28.14% sleep [kernel.vmlinux] [k] __rb_erase_color 27.21% sleep [kernel.vmlinux] [k] unmap_page_range 27.20% sleep ld-2.29.so [.] __tunable_get_val 15.24% sleep [kernel.vmlinux] [k] thp_get_unmapped_area 1.96% perf [kernel.vmlinux] [k] perf_event_exec 0.22% perf [kernel.vmlinux] [k] native_sched_clock 0.02% perf [kernel.vmlinux] [k] intel_bts_enable_local 0.00% perf [kernel.vmlinux] [k] native_write_msr # # (Tip: Boolean options have negative forms, e.g.: perf report --no-children) # $ Reported-by: Arnaldo Carvalho de Melo Signed-off-by: Igor Lubashev Tested-by: Arnaldo Carvalho de Melo Tested-by: Mathieu Poirier Cc: Alexander Shishkin Cc: Alexey Budankov Cc: James Morris Cc: Jiri Olsa Cc: Namhyung Kim Cc: Peter Zijlstra Cc: Suzuki Poulouse Cc: linux-arm-kernel@lists.infradead.org Link: http://lkml.kernel.org/r/1566869956-7154-4-git-send-email-ilubashe@akamai.com Signed-off-by: Arnaldo Carvalho de Melo --- tools/perf/util/evsel.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/util/evsel.c b/tools/perf/util/evsel.c index 7c704b8..d4540bf 100644 --- a/tools/perf/util/evsel.c +++ b/tools/perf/util/evsel.c @@ -282,7 +282,7 @@ struct evsel *perf_evsel__new_idx(struct perf_event_attr *attr, int idx) static bool perf_event_can_profile_kernel(void) { - return perf_event_paranoid_check(-1); + return perf_event_paranoid_check(1); } struct evsel *perf_evsel__new_cycles(bool precise) -- 2.7.4