Cyclicload program is designed to simulate load at regular intervals in form of one or two threads. Signed-off-by: Priyanka Jain <Priyanka.Jain@xxxxxxxxxxxxx> --- src/cyclictest/README_cyclicload | 147 ++++++++++++++++++++++++++++++++++++++ 1 files changed, 147 insertions(+), 0 deletions(-) create mode 100644 src/cyclictest/README_cyclicload diff --git a/src/cyclictest/README_cyclicload b/src/cyclictest/README_cyclicload new file mode 100644 index 0000000..f1e99bf --- /dev/null +++ b/src/cyclictest/README_cyclicload @@ -0,0 +1,147 @@ +DESCRIPTION +------------- + +The cyclicload program is developed above existing cyclictest application. +It is basically designed to simulate specified load at regular intervals +in addition to cyclictest functionality. +It can simulate one or two load threads. + + +Why it is required? +--------------------- +It is required to test system performance under a specified load +along with tracking latency of simulated load thread. + + +Example use case +-------------------- +For products like LTE, L2 layer runs in form of two threads. +-MAC layer thread runs at highest RT priority producing a +fixed load at regular intervals and +-second thread run at lower RT priority or in non-rt priority + producing some load in each interval depending upon availability of CPU. +Requirement is to test system under this load as well as to +track latency of highest priority RT thread which is MAC thread +in example usecase. + + +What does it do? +------------------ +It creates one or two load generating thread/s. +1)load1 thread (timer thread) +2)load2 thread +priority, nice value, load % as input via command line + +-cyclictest funcationality like latency measurement + + +How does it work +----------------- +It uses generate_load loop function to simualte load. +First it caliberate required loop_count per unit time per CPU. +It stores this data in some file. +For subsequent runs, it uses this caliberated data to generate load +if form of one or two threads . +It keeps on tracking the latency of RT thread. +More in Design Overview section. + + +Recommended Settings +---------------------- +-First run is recommended to be run with no or least load for accuracy. +-should be run with sudo or root permission. +-caliberation routine produces calinerate_ount file in runnign directory. + If one don't have permission in that dir, path should be changed in + FILENAME or one can exploit shared memory method. +-Atleast one thread should be of RT priority. This thread takes priority of + cyclictest as its priority. +-cyclictest applcication should be run with SCHED_OTHER policy. +-recommended to run in quiet mode (-q) in background. +TODO: add option to take filepath from cmd line + + +Cmd line usage/examples +------------------------ +New command line arguments: + "-x --load_t1 load in percentage for t1 thread\n" + "-X --load_t2 load in percentage for t2 thread\n" + "-z --priority_t2 priority of t2 thread\n" + "-Z --nice_t2 nice value of t2 thread\n" + +If both load_t1 and load_t2 are zero, it behaves as default cyclictest application + +For uniprocessor: + #sudo ./cyclictest -p 99 -c 1 -d 0 -x 40 -X 30 -q -D 600& + +For multiprocessor: + #sudo ./cyclcitest -p 99 -c 1 -d 0 -x 40 -X 30 -q -D 600 -S& + + + +Future Enhancements +------------------- +Maintain statistics of average load produces. +invalidate cache in each interval to make it close to actual scenario. +can be scalable to produce n number of load threads. + + +Design Overview +-------------- +--------------- + +The logic to simulate load has been added above existing cyclictest application. + +Threads +-------- +cyclicload : main process +-------------------------- +-parse input arguments. + +-for first run : create caliberate thread. + store caliberated count in caliberate_count file +-for subsequent runs: + read caliberated count from file and use that count to simulate defined load. + +-create t load1threads (t depending on cmdlime args, for smp system = num of cores, one thread per core) + +-update stats periodically while !shutdown +-print stats periodically depending on cmdline args while !shutdown + + +caliberate thread +------------------ +-is created only once for the first run of cyclicload +-run at highest RT priority. +-affine itself turn by turn to each cpu. (for all cpus for multicore system) +-caliberate count per unit (ms by default) per cpu +-store per cpu data in caliberate_count_array +-recommended to be run with no or least load. + + +load1 thread(timer thread) +--------------------------- +-run at priority parsed in main routine +-recommended to run at highest RT priority +-creates load2_thread (optional only if on load2 is nonzero) +-calculate number of loops to execute to generate defined load by + using caliberate_count_array and load percentage parsed in main routine +-reduced interval = interval(window) - duration for load_t1 +-while loop until !shutdown + -generate load_t1 load + -sleep for reduced interval + -calculate latency (cosumes around 1%-2% cpu) + -discard off remaining load if window expires + -set next_window_started flag to 1 + -signal load2_thread about next window +-overhead: consumes 1-2% cpu for latency maintainenance, etc +-variation in produced load : 0%-2% of full cpu utilization + + +load2_thread +------------ +generate load_t2 load +wait for next window to start +if window expires before generate load_t2 finishes, + discard off remaining load + restart generate load_t2 load +variation in produced load : 0%-1% of full cpu utilization -- 1.7.4.1 -- To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
