From 94c7eb54c4b8e81618ec79f414fe1ca5767f9720 Mon Sep 17 00:00:00 2001 From: Eric Dumazet Date: Thu, 13 Aug 2020 10:06:43 -0700 Subject: [PATCH] random32: add a tracepoint for prandom_u32() There has been some heat around prandom_u32() lately, and some people were wondering if there was a simple way to determine how often it was used, before considering making it maybe 10 times more expensive. This tracepoint exports the generated pseudo random value. Tested: perf list | grep prandom_u32 random:prandom_u32 [Tracepoint event] perf record -a [-g] [-C1] -e random:prandom_u32 sleep 1 [ perf record: Woken up 0 times to write data ] [ perf record: Captured and wrote 259.748 MB perf.data (924087 samples) ] perf report --nochildren ... 97.67% ksoftirqd/1 [kernel.vmlinux] [k] prandom_u32 | ---prandom_u32 prandom_u32 | |--48.86%--tcp_v4_syn_recv_sock | tcp_check_req | tcp_v4_rcv | ... --48.81%--tcp_conn_request tcp_v4_conn_request tcp_rcv_state_process ... perf script Signed-off-by: Eric Dumazet Cc: Willy Tarreau Cc: Sedat Dilek Tested-by: Sedat Dilek Signed-off-by: David S. Miller --- include/trace/events/random.h | 17 +++++++++++++++++ lib/random32.c | 2 ++ 2 files changed, 19 insertions(+) diff --git a/include/trace/events/random.h b/include/trace/events/random.h index 32c10a515e2d..9570a10cb949 100644 --- a/include/trace/events/random.h +++ b/include/trace/events/random.h @@ -307,6 +307,23 @@ TRACE_EVENT(urandom_read, __entry->pool_left, __entry->input_left) ); +TRACE_EVENT(prandom_u32, + + TP_PROTO(unsigned int ret), + + TP_ARGS(ret), + + TP_STRUCT__entry( + __field( unsigned int, ret) + ), + + TP_fast_assign( + __entry->ret = ret; + ), + + TP_printk("ret=%u" , __entry->ret) +); + #endif /* _TRACE_RANDOM_H */ /* This part must be outside protection */ diff --git a/lib/random32.c b/lib/random32.c index 3d749abb9e80..932345323af0 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -39,6 +39,7 @@ #include #include #include +#include #ifdef CONFIG_RANDOM32_SELFTEST static void __init prandom_state_selftest(void); @@ -82,6 +83,7 @@ u32 prandom_u32(void) u32 res; res = prandom_u32_state(state); + trace_prandom_u32(res); put_cpu_var(net_rand_state); return res; -- 2.11.0