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Detours. On a time-sharing system, a process is interrupted at any time. time. Detour is time period not for a target process, which contains. kernel service scheduler,memory management,network subsystem,etc other process etc cache miss, TLB miss. Record each detour in precious. start1.

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Presentation Transcript
slide1
Detours

On a time-sharing system, a process is interrupted at any time.

time

Detour is time period not for a target process, which contains

  • kernel service
    • scheduler,memory management,network subsystem,etc
  • other process
  • etc
    • cache miss, TLB miss
slide2
Record each detour in precious

start1

start2

start3

start4

...

...

startN

time

duration1

duration2

duration3

duration3

durationN

record detours

detour recorder

output a recorded data

# HEADERS

# TICKS_PER_SECOND

# ...

start1 duration1

start2 duration2

start3 duration3

.....

slide3
Detour Recording Logic idea

[Basic Idea – meta code]

rdtsc() is called frequently

Some experimental results,

Running code at

BG/L IO node

700MHz PowerPC

Linux 2.4.19 based kernel

rdtsc() is called every 0.1usec

Minimum detour activety

is 1.8 usec, which is timer update.

If array is 2000 in size(1000 detours),

it can record approx. 10 sec.

current = rdtsc();

while( array is not full ) {

prev = current;

current = rdtsc();

if( current – prev > precision ) {

array.push_back(prev);

array.push_back(current);

}

}

slide5
Graph – sorted by detour duration

60ms

periodic event

10ms

periodic event

slide6
Detours in fixed time quantum

time

Detours

Q

Total detour in Q

Sync Frequency = 1/Q (HZ)

slide7
A node in parallel machine has detour.

Detour distribution is same as single machine.

node1

node2

node3

nodeN-1

nodeN

pick detour randomly

from single node experimental.

fixed time

record

changing

sync. freq.

slide8
Simulation algorithm for parallel machine

(from a single node data)

node1

node2

node3

nodeN-1

nodeN

max(D)-min(D)

try 1

d1

d2

d3

dN-1

dN

max(D)-min(D)

try 1

d1

d2

d3

dN-1

dN

max(D)-min(D)

try M

d1

d2

d3

dN-1

dN

[Input]

recorded data

N=machine size

M=try count

F=Sync Frequency

[Output]

average and standard deviation

of {max(D)-min(D)}

what we know so far
What we know so far
  • maximum detour(latency) is a matter of parallel perfomance
    • minimize the max latency increase the parallel performance
  • linux kernel may be good for parallel machine
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