UNIVERSITY OF NIVERSITY OF MASSACHUSETTS ASSACHUSETTS, A , AMHERST • MHERST • Department of Computer Science Department of Computer Science Matthew Hertz, Yi Feng, & Emery Berger Department of Computer Science University of Massachusetts Hippocratic Garbage Collection
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U NIVERSITY OF M ASSACHUSETTS, A MHERST Department of Computer Science Matthew Hertz, Yi Feng, & Emery Berger Department of Computer Science University.
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UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science
Matthew Hertz, Yi Feng, & Emery Berger
Department of Computer ScienceUniversity of Massachusetts
Hippocratic Garbage Collection
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 2
Dude, where’s my performance?
Sun HotSpot JDK 1.4.1, Java Beans benchmark
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 3
Ever-Steeper Memory Hierarchy
Higher = smaller, faster, closer to CPU A real desktop machine (mine)
registers
L1 cache
L2 cache
RAM
Disk
8 integer, 8 floating-point; 1-cycle latency
8K data & instructions; 2-cycle latency
512K; 7-cycle latency
1GB; 100 cycle latency
40 GB; 38,000,000 cycle latency (!)
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 4
Program Throughput: Ideal vs. Real
492 113 103 930
100
200
300
400
500
600
700
800
900
1000
Execution Time for pseudoJBB with 60MB Heap
IdealGenCopyGenMS
Available Memory (in MB)
Exe
cuti
on T
ime (
in s
)
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 5
GC Pause Time
492 113 103 930
5
10
15
20
25
30
35
Max Garbage Collection Pause for pseudoJBB
GenCopyGenMS
Available Memory (in MB)
Avg.
GC
Pause
(in
s)
From 55 milliseconds to 30 seconds!..Can we avoid this?
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 6
Memory Prices Over TimeRAM Prices Over Time
(1977 dollars)
$0.01
$0.10
$1.00
$10.00
$100.00
$1,000.00
$10,000.00
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
Year
Do
llars
per
GB
2K
8K
32K
128K
512K
2M
8M
conventional DRAM
“Soon it will be free…”
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 7
Memory Prices: Inflection Point
RAM Prices Over Time(1977 dollars)
$0.01
$0.10
$1.00
$10.00
$100.00
$1,000.00
$10,000.00
1977
1978
1979
1980
1981
1982
1983
1984
1985
1986
1987
1988
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
Year
Do
llars
per
GB
2K
8K
32K
128K
512K
2M
8M
512M
1G
SDRAM,RDRAM,DDR,Chipkill
conventional DRAM
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 8
Memory Not So Free
Servers: buy 4GB,get 1 CPU free!
Sun E10000: 4GB extra = $75,000!
Fast RAM Cosmic rays…
4GB Sun RAM = ½ Ferrari Modena
“Buy more RAM” = “Ferraris for Everyone”
Desktops: most 256MB 1GB = 50% more $ Laptops = 70%, if possible
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 9
Fast DDR2 modules today: $500/GB
UUNIVERSITY OF NIVERSITY OF MMASSACHUSETTSASSACHUSETTS, A, AMHERST • MHERST • Department of Computer Science Department of Computer Science 10