From: Arnaldo Carvalho de Melo <[email protected]> Using 4 kHz is not necessary and sometimes is more than what was auto-tuned:
# dmesg | grep max_sample_rate | tail -2 [ 2499.144373] perf interrupt took too long (2501 > 2500), lowering kernel.perf_event_max_sample_rate to 50000 [ 3592.413606] perf interrupt took too long (5069 > 5000), lowering kernel.perf_event_max_sample_rate to 25000 Simulating a auto-tune of 2000 we make the test fail, as reported by Steven Noonan for one of his machines, so reduce it to 500 HZ, it is enough to get a good number of samples for this test: # perf test -v 21 2>&1 | grep '^Reading object code for memory address' | tee /tmp/out | tail -5 Reading object code for memory address: 0x479f40 Reading object code for memory address: 0x7f29b7eea80d Reading object code for memory address: 0x7f29b7eea80d Reading object code for memory address: 0x7f29b7eea800 Reading object code for memory address: 0xffffffff813b2f23 [root@jouet ~]# wc -l /tmp/out 40 /tmp/out [root@jouet ~]# For systems that auto-tune below that, the previous patches will tell the user what is happening so that he may either ignore the result of this test or bump /proc/sys/kernel/perf_event_max_sample_rate. Cc: Adrian Hunter <[email protected]> Cc: Jiri Olsa <[email protected]> Cc: Namhyung Kim <[email protected]> Cc: Steven Noonan <[email protected]> Cc: Wang Nan <[email protected]> Link: http://lkml.kernel.org/n/[email protected] Signed-off-by: Arnaldo Carvalho de Melo <[email protected]> --- tools/perf/tests/code-reading.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/tools/perf/tests/code-reading.c b/tools/perf/tests/code-reading.c index f84339cb7f95..afc9ad0a0515 100644 --- a/tools/perf/tests/code-reading.c +++ b/tools/perf/tests/code-reading.c @@ -439,7 +439,7 @@ static int do_test_code_reading(bool try_kcore) .mmap_pages = UINT_MAX, .user_freq = UINT_MAX, .user_interval = ULLONG_MAX, - .freq = 4000, + .freq = 500, .target = { .uses_mmap = true, }, -- 2.5.0
