plasma control system (PCS) server environment based on MRG-R - - PowerPoint PPT Presentation

Performance test of new real time plasma control system (PCS) server environment based on MRG-R

Yeonjung Kima, S. H. Hahna, W. R. Leea, H.Hana,

• M. H. Wooa, B. G. Penaflorb and
• Y. S. Baea

aNational Fusion Research Institute(NFRI), Daejeon, Korea bGeneral Atomics, San Diego, CA, USA

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1 . Introduction

• Why Performance T

est ?

• MRG-R
• 2. Method for MRG-R System Tuning
• 3. Conditions for Performance T

est

• Input values & setting
• Measurement of Time Register
• 4. Results of Performance T

est

• 5. Summary and Future Plan

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Table of Contents

 Why the performance test ?

• The real-time control environment of KSTAR Plasma Control

System(PCS) requires fast control cycles up to 20 KHz, which is very difficult to support at the standard Linux OS scheduler.

• KSTAR uses a customized Linux kernel which is not influenced by

any external interrupts in the real-time operation mode(rtmode).

• The MRG-R[http://www.redhat.com/products/mrg/realtime] is an

ITER-compatible real-time Operation System (OS) which showed the most excellent performance.

• We want to confirm that the MRG-R is suitable as the real-

time OS environment for the KSTAR PCS.

Introduction(1)

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 Red Hat Enterprise MRG Realtime (MRG-R)

• BENEFITS & FEATURES of MRG-R
• Highly deterministic performance
• High-resolution actions
• Full application compatibility with standard Red Hat

Enterprise Linux.

• Uninterrupted services for high-priority processes.
• MRG-R replaces the standard Red Hat Enterprise Linux

kernel in order to provide extra support for real-time computing.

Introduction(2)

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MRG-R System Tuning (1)

 PCSRT6 Version : RHEL 6.3 (2.6.32-279.el6.x86_64) MRG-R (3.8.13-rt27.33.el6rt.x86_64)  Disable the graphic desktop: Set runlevel 3  Disable the irqbalance deamon

• Use chkconfig to ensure that irqbalance does not restart on boot.
• Open /etc/sysconfig/irqbalance in editor and find the section of the

file titled FOLLOW_ISOLCPUS and remove the # character.

• change the values to yes.

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MRG-R System Tunning(2)

 Booting by the MRG Realtime kernel

(a) Open the /etc/grub.conf file and add crashkernel =128M (b) Add the parameter for TSC timer synchronizaton clocksource=tsc powernow-k8.tscsysn=1 (c) isolcpus = 13-23 is boot kernel option for CPU isolation.

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Conditions for Performance T est(1)

 Run the test program (testrtmode.c) at the isolated CPU to match the conditions of KSTAR RT process running  Input values setting

• CPU number =13
• Test period for test program (NUMSECOND)=5 seconds

 Main settings

• Number of sample cycles : 5000 or 20000cycle
• Threshold value (=unit for control cycle) : 1/10/20/50 µs

 Method of performance measurement

• Measures total running time more than the threshold value.
• Do the test for threshold 10/20/50µs as well.

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Conditions for Performance T est(2)

 Measurement of total running time by the Time Register

• Use the internal 64-bit clock counter as the time register.
• Read into Register(EDX:EAX) using the instruction of RDTSC

(read time stamp counter)[http://en.wikipedia.org/wiki/Time_Stamp_Counter]

• Using the readclock() function call , get the count values.
• Counters are converted as physical time using the CPU clock
• cycle. (For pcsrt6, the CPU clock cycle is measured as 2300MHz)

 Calculation of the total running time

• total count values is divided by CLOCKMICROSECOND(2300)

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Conditions for Performance T est(3)

* Optimization of test program (testrtmode.c) while (NUMSECOND & max_sample_cnt< MAX_SAMPLE ) {

Readtick(t_diff= t_current - t_last); /* get the count values of each section */ total_clock_val=+ t_diff; /*accumulation of running count values */ max_sample_cnt++; If(t_diff > THRESHOLD*CLOCKMICROSECOND) /* excess threshold*/ { save_elapsed_seconds[num_delays] = elapsed_seconds save_elapsed_milliseconds[num_delays] = elapsed_milliseconds save_t_diffs[num_delays] =t_diff/CLOCKMICROSECONDS; save_excess_time += save_t_diffs[num_delays]; num_delays++; /* number of excess threshold values */ } else num_lower_delays++; /* number of less than threshold values */ }

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Conditions for Performance T est(4)

 Explain the Variable used the test program(testrtmode.c)

Variable & synonym explain CLOCKMICROSECOND CPU clock cycle per 1µs =2300 max_sample_cnt MAX_SAMPLE(synonym) sample cycle(synonym) num_delays + num_lower_delay total_running_time Response time (synonym) Total_clock_val /CLOCKMICROSECOND average_excess_cnt average excess rate(synonym) (num_delays/max_sample_cnt)*100

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Results of Performance T est(1)

 Result of test

• Basic test: only measure the counters
• Dummy load test : add the additional load using a printf()

between two measurements in repetitive statement while().

• Expected Total Running Time

Threshold ( µs) sample 5000 cycle Sample 20000cycle 1µs 5000 µs 20000 µs 10µs 50000 µs 200000 µs 20µs 100000 µs 400000 µs 50µs 250000 µs 10000000 µs

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Results of Performance T est(2)

Threshold ( µs) sample 5000 cycle Sample 20000cycle 1µs 0 % 0 ~0.01% 10µs 0 % 0 % 20µs 0 % 0 % 50µs 0 % 0 %

• No sample cycles behind the threshold are found at the first

5000 sample cycles

• 0.01% of sample cycles behind the threshold are found at the

first 20000 sample cycles at threshold 1µs (20% of total test number)

• From the basic test, the MRG-R environment is capable to

perform a single process up to 10µs(=100 kHz) of the control cycles without delay

• Average excess rate of basic test

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* Total test number is 10 times *

Results of Performance T est(2)

• Minimum value is 0, Maximum value is 89.
• Addition of the printf() (calls interrupts for display) makes the

test program performance slower

• However, the test program did not have performance delay up

to 10 µs of control cycle by the additional dummy load

• The 1 µs threshold is seriously affected by this interrupt calling

Threshold ( µs) sample 5000 cycle Sample 20000cycle 1µs 0~56 % 0~89% 10µs 0 % 0 % 20µs 0 % 0 % 50µs 0 % 0 %

• Average excess rate of dummy test

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* Number of total test is 10 times *

Summary and Future Plan

 Performance test for real-time PCS process under MRG-realtime (MRG-R) environment is done at pcsrt6 system.  The system is optimized following the official tuning guide of MRG-R  A special test program of measuring response time is used for testing performance at control cycles of 1/10/20/50 us  For a single isolated process, the MRG-R is capable of safely running control cycles up to 10 us  Future plan :  Test compatibility of the communication hardware (RFM or digitizer)  Test performace of the new PCS process for NTM mode detection acquisition

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