Embed Size (px)
DESCRIPTION
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June 4, Return-Address-Stack (RAS) return from printf main(): my_printf() my_function() my_printf() return main: my_printf() my_function() my_printf() return function calls push return address on RAS 1 my_printf() RAS return from printf my_printf: for(condition){ printf() } return printf() TOS printf: /* print */ return returns predicted by popping from RAS 2 return from my_printf return from my_printf return from my_function return from main my_function: /* fun */ return my_function()
Citation preview
Correct Alignment of a RAS after Call and Return Mispredictions
Ghent University
Veerle DesmetYiannakis Sazeides
Constantinos KourouyiannisKoen De Bosschere
University of Cyprus
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 2
MotivationReturn-Address-Stack (RAS)
1. Correct alignment2. Effect deeper pipelines
byVeerle Desmet
Ghent University
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 3
Return-Address-Stack (RAS)
return fromprintf
main():my_printf()my_function()
my_printf()return
main: my_printf() my_function() my_printf()return
function calls pushreturn address on RAS
1
my_printf()
RAS
return fromprintf
my_printf: for(condition){
printf() }return
printf()
TOS
printf: /* print */return
returns predicted by popping from RAS
2return frommy_printf
return frommy_printf
return frommy_functionreturn from
main
my_function: /* fun */return
my_function()
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 4
Mispredictionsfe
tch
chec
kpoi
nt
RASreturn from
printfTOS return from
my_printfreturn from
main
recovery
wrong path
Speculative RAS updates due to wrong path calls
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 5
Bottlenecks for RAS performance
De-alignment`unbalanced # of
call/return’
Corruption`RAS content
overwritten by wrong path calls’
Overflow`call depth exceeds stack
size’
return frommain
return fromprintf
RAS
return frommy_printf
return frommy_printf
TOS TOS
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 6
Correct Alignment…
RAS
return fromprintf
return frommain
TOS
Checkpoint TOS1
Conditional branch misprediction2
Wrong path3
Recovery to checkpointed TOS4
return fromwrong path
e.g. 1 misspeculated call
return fromwrong pathreturn frommy_function
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 7
… after Call Mispredictions
RAS
return fromprintf
return frommain
TOS
Checkpoint TOS1
Call target misprediction + RAS update2
Wrong path3
Recovery to checkpointed TOS4
e.g. 1 misspeculated call
return frommy_function
return fromwrong pathreturn fromwrong pathreturn frommispr. call
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 8
… after Return Mispredictions
RAS
return fromprintf
TOS
Checkpoint TOS1
Return target misprediction + RAS update2
Wrong path3
Recovery to checkpointed TOS4
e.g. no misspeculated calls or returns
return frommispr returnreturn frommispr returnreturn from
main
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 9
return fromprintf
TOS
return frommispred call
Correct Alignment Incorrect Alignment
Correct Alignment
TOS TOS mispred.return addr
Conditional branch misprediction
Callmisprediction
Returnmisprediction
RAS RAS RAS
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 10
Correct Alignment
0%5%
10%15%20%
25%30%
com
pres
s95
gcc9
5
go95
ijpeg
95 li95
m88
ksim
95
vorte
x95
mcf
00
pars
er00
vorte
x00
mes
a00
aver
age
RAS misprediction rate
0,940,960,981,001,021,041,061,081,101,12
com
pres
s95
gcc9
5
go95
ijpeg
95 li95
m88
ksim
95
vorte
x95
mcf
00
pars
er00
vorte
x00
mes
a00
aver
age
Speedup
Incorrect Alignment
Correct AlignmentSpeedup can be affected by up to 10%
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 11
A lot of published work…SimpleScalar
HydraScalar
Yeh, Intel patent
SimWattchSimca
Jourdan Eickemeyer,Hoyt,
Hummel,McDonald,McMahan
Steely
INCORRECT=
LOWER PERFORMING
CORRECTUNCLEAR
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 12
Bottlenecks for RAS performance
De-alignment`unbalanced # of
call/return’
Corruption`RAS content
overwritten by wrong path calls’
Overflow`call depth exceeds stack
size’
return frommain
return fromprintf
RAS
return frommy_printf
return frommy_printf
TOS TOS
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 13
RAS content recovery
0,900,95
1,001,051,10
1,151,20
com
pres
s95
gcc9
5
go95
ijpeg
95 li95
m88
ksim
95
vorte
x95
mcf
00
pars
er00
vorte
x00
mes
a00
aver
age
Speedup
Incorrect Alignment
Correct Alignment
Also checkpoints/recoverstop of stack data
2% speedup on average
[Skadron et al. @ MICRO 1998]
top of stackdata
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 14
MotivationReturn-Address-Stack (RAS)
1. Correct alignment2. Effect deeper pipelines
byVeerle Desmet
Ghent University
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 15
Deeper Pipelines…
0,880,900,920,940,960,981,00
5 10 15 20 25 30pipeline stages
relative IPC to full RAS recovery
32-entry RAS16-entry RAS
8-entry RAS
64-entry RAS
On average, reasonable scaling…
Independence on RAS size
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 16
But... per benchmark
0,88
0,9
0,92
0,94
0,96
0,98
1
1,02
com
pres
s95
gcc9
5
go95
ijpeg
95 li95
m88
ksim
95
vorte
x95
mcf
00
parser00
vorte
x00
mes
a00
aver
age
rela
tive
IPC
to fu
ll RA
S re
cove
ry
-7% -5%32-entry RAS 15 stages
10 stages5 stages
20 stages25 stages30 stages
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 17
RAS
Corruptions per kilo instructions
tos tos tos tos tos tos1 1 1 1 1 130 30 30 30 30 303131 31 31 31 31
0
1
2
3
4
5
6
7
8
5 10 15 20 25 30
pipeline stages
32-entry RAS
…
Backward (tos,1,…) more destructive
than forward corruption (31,30,…)
31tos12
34
30
corruptiondistance
1
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 18
Individual benchmarks
tos tos
tos
tostos tos tos
tos
11
1
223
2829
30 30
30
3131
31
31
31
31
31
tos
11
129
30
30
31 310
1
2
3
4
5
6
7
8co
mpr
ess9
5
gcc9
5
go95
ijpeg
95 li95
m88
ksim
95
vorte
x95
mcf
00
pars
er00
vorte
x00
mes
a00R
AS
cor
rupt
ions
per
kilo
inst
ruct
ions 32-entry RAS
20 stage pipeline
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 19
TOS behavior
time li95gcc95 time
32-entry RAS20 stage pipeline
Mainly forward corruption More backward corruption
wrong path RAS updates
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 20
Bottlenecks for RAS performance
De-alignment`unbalanced # of
call/return’
Corruption`RAS content
overwritten by wrong path calls’
Overflow`call depth exceeds stack
size’
return frommain
return fromprintf
RAS
return frommy_printf
return frommy_printf
TOS TOS
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 21
TOS Behaviorno overflow
32-entry RAS20 stage pipeline
timetime li95gcc95
overflow
Workshop on Duplicating Deconstructing and Debunking (WDDD 2005) --- June
4, 2005 22
Summary Correct Aligned RAS
Return misprediction decrease with 40% Speedup of up to 10%
Deeper Pipelines One of the best performing RAS recovery techniques
Satisfactory on average Performance decrease up to 7% for some programs
May need to checkpoint more content Paper:
Possible implementations Call uncorruption optimization for free How to fix correct alignment in SimpleScalar
Correct Alignment of a RAS after Call and Return Mispredictions
Ghent University
Veerle DesmetYiannakis Sazeides
Constantinos KourouyiannisKoen De Bosschere
University of Cyprus
