09_multicore-1up

# 09_multicore-1up - CIS 501 Computer Architecture Unit 9:...

This preview shows pages 1–11. Sign up to view the full content.

CIS 501 (Martin): Multicore 1 CIS 501 Computer Architecture Unit 9: Multicore (Shared Memory Multiprocessors) Slides originally developed by Amir Roth with contributions by Milo Martin at University of Pennsylvania with sources that included University of Wisconsin slides by Mark Hill, Guri Sohi, Jim Smith, and David Wood.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Mem CIS 501 (Martin): Multicore 2 This Unit: Shared Memory Multiprocessors • Thread-level parallelism (TLP) • Shared memory model • Multiplexed uniprocessor • Hardware multihreading • Multiprocessing • Synchronization • Lock implementation • Locking gotchas • Cache coherence • Bus-based protocols • Directory protocols • Memory consistency models CPU I/O System software App App App CPU CPU CPU CPU CPU
Readings • Textbook (MA:FSPTCM) Sections 7.0, 7.1.3, 7.2-7.4 Section 8.2 CIS 501 (Martin): Multicore 3

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Beyond Implicit Parallelism • Consider “daxpy”: daxpy(double *x, double *y, double *z, double a): for (i = 0; i < SIZE; i++) Z[i] = a*x[i] + y[i]; • Lots of instruction-level parallelism (ILP) • Great! • But how much can we really exploit? 4 wide? 8 wide? • Limits to (efficient) super-scalar execution • But, if SIZE is 10,000, the loop has 10,000-way parallelism! • How do we exploit it? CIS 501 (Martin): Multicore 4
Explicit Parallelism • Consider “daxpy”: daxpy(double *x, double *y, double *z, double a): for (i = 0; i < SIZE; i++) Z[i] = a*x[i] + y[i]; • Break it up into N “chunks” on N cores! • Done by the programmer (or maybe a really smart compiler) daxpy( int chunk_id , double *x, double *y, *z, double a): chuck_size = SIZE / N my_start = chuck_id * chuck_size my_end = my_start + chuck_size for (i = my_start; i < my_end; i++) z[i] = a*x[i] + y[i] Assumes Local variables are “private” and x, y, and z are “shared” Assumes SIZE is a multiple of N (that is, SIZE % N == 0) CIS 501 (Martin): Multicore 5 Chunk ID Start End 0 0 99 1 100 199 2 200 299 3 300 399 SIZE = 400, N=4

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
CIS 501 (Martin): Multicore 6 Multiplying Performance • A single processor can only be so fast • Limited clock frequency • Limited instruction-level parallelism • Limited cache hierarchy • What if we need even more computing power? • Use multiple processors! • But how? • High-end example: Sun Ultra Enterprise 25k • 72 UltraSPARC IV+ processors, 1.5Ghz • 1024 GBs of memory • Niche: large database servers • \$\$\$
CIS 501 (Martin): Multicore 7 Multicore: Mainstream Multiprocessors Multicore chips IBM Power5 • Two 2+GHz PowerPC cores • Shared 1.5 MB L2, L3 tags • AMD Quad Phenom • Four 2+ GHz cores • Per-core 512KB L2 cache • Shared 2MB L3 cache • Intel Core i7 Quad • Four cores, private L2s • Shared 6 MB L3 • Sun Niagara • 8 cores, each 4-way threaded • Shared 2MB L2, shared FP • For servers, not desktop 1.5MB L2 L3 tags Core 1 Core 2 Why multicore? What else would you do with 1 billion transistors?

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
Sun Niagara II CIS 501 (Martin): Multicore 8
Intel Quad-Core “Core i7” CIS 501 (Martin): Multicore 9

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
CIS 501 (Martin): Multicore 10 Application Domains for Multiprocessors Scientific computing/supercomputing • Examples: weather simulation, aerodynamics, protein folding
This is the end of the preview. Sign up to access the rest of the document.

## This note was uploaded on 10/19/2011 for the course CS 501 taught by Professor Matin during the Fall '10 term at UPenn.

### Page1 / 128

09_multicore-1up - CIS 501 Computer Architecture Unit 9:...

This preview shows document pages 1 - 11. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online