On Wed, Mar 6, 2019 at 7:27 PM Peter Zijlstra <[email protected]> wrote: > > On Wed, Mar 06, 2019 at 06:15:39PM +0800, Yafang Shao wrote: > > On Wed, Mar 6, 2019 at 6:09 PM Peter Zijlstra <[email protected]> wrote: > > > > > > On Wed, Mar 06, 2019 at 04:43:46PM +0800, Yafang Shao wrote: > > > > When I'm using trace_sched_stat_{iowait, blocked, wait, sleep} to > > > > measure how long the processes are stalled, there's always no output > > > > from > > > > trace_pipe while there're really some tasks in uninterruptible sleep > > > > state. That makes me confused, so I try to investigate why. > > > > Finally I find the reason is that CONFIG_SCHEDSTATS is not set. > > > > > > > > To avoid such kind of confusion, we should not expose these tracepoints > > > > if CONFIG_SCHEDSTATS is not set. > > > > > > Yeah, lets not sprinkle #ifdef. Big fat NAK. > > > > > > Also, the below seem to indicate your compiler is stupid. Without > > > CONFIG_SCHEDSTAT, schedstat_enabled() should be a constant 0 and DCE > > > should delete all code. > > > > > > > My compiler is GCC-7.3.0. > > I don't know which comipler could be smart enough to remove the > > definition of these tracepoints. > > Could you pls. tell me what compiler you are using ? > > Just look at the generated code...
When CONFIG_SCHEDSTATS is not set, I have objdumped the vmlinux, and the perf_trace_sched_stat_template is still there withou my patch. $ objdump -D vmlinux > vmlinux.asm $ cat vmlinux.asm | grep trace_sched_stat ffffffff810b3b40 <perf_trace_sched_stat_template>: ... So I can't get your point really. Forgive me if I missed something. Thanks Yafang
