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path: root/kernel/trace/trace_benchmark.c
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2014-06-06tracing: Only calculate stats of tracepoint benchmarks for 2^32 timesSteven Rostedt (Red Hat)
When calculating the average and standard deviation, it is required that the count be less than UINT_MAX, otherwise the do_div() will get undefined results. After 2^32 counts of data, the average and standard deviation should pretty much be set anyway. Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-06-05tracing: Convert stddev into u64 in tracepoint benchmarkSteven Rostedt (Red Hat)
I've been told that do_div() expects an unsigned 64 bit number, and is undefined if a signed is used. This gave a warning on the MIPS build. I'm not sure if a signed 64 bit dividend is really an issue or not, but the calculation this is used for is standard deviation, and that isn't going to be negative. We can just convert it to unsigned and be safe. Reported-by: David Daney <ddaney.cavm@gmail.com> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-06-04tracing: Remove unused variable in trace_benchmarkSteven Rostedt (Red Hat)
Somehow this unused variable warning sneaked past my warnings check (probably due to it depending on a new config). kernel/trace/trace_benchmark.c: In function 'trace_do_benchmark': kernel/trace/trace_benchmark.c:38:6: warning: unused variable 'seedsq' [-Wunused-variable] u64 seedsq; ^ Link: http://lkml.kernel.org/r/20140604160921.4f4e69c4@canb.auug.org.au Reported-by: Stephen Rothwell <sfr@canb.auug.org.au> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
2014-05-29tracing: Add tracepoint benchmark tracepointSteven Rostedt (Red Hat)
In order to help benchmark the time tracepoints take, a new config option is added called CONFIG_TRACEPOINT_BENCHMARK. When this option is set a tracepoint is created called "benchmark:benchmark_event". When the tracepoint is enabled, it kicks off a kernel thread that goes into an infinite loop (calling cond_sched() to let other tasks run), and calls the tracepoint. Each iteration will record the time it took to write to the tracepoint and the next iteration that data will be passed to the tracepoint itself. That is, the tracepoint will report the time it took to do the previous tracepoint. The string written to the tracepoint is a static string of 128 bytes to keep the time the same. The initial string is simply a write of "START". The second string records the cold cache time of the first write which is not added to the rest of the calculations. As it is a tight loop, it benchmarks as hot cache. That's fine because we care most about hot paths that are probably in cache already. An example of the output: START first=3672 [COLD CACHED] last=632 first=3672 max=632 min=632 avg=316 std=446 std^2=199712 last=278 first=3672 max=632 min=278 avg=303 std=316 std^2=100337 last=277 first=3672 max=632 min=277 avg=296 std=258 std^2=67064 last=273 first=3672 max=632 min=273 avg=292 std=224 std^2=50411 last=273 first=3672 max=632 min=273 avg=288 std=200 std^2=40389 last=281 first=3672 max=632 min=273 avg=287 std=183 std^2=33666 Signed-off-by: Steven Rostedt <rostedt@goodmis.org>