SLIDE 1
Motivation: Smart-phones
Smart-phones becoming ubiquitous DRAM Memory consumes up to 30%
- f system power
Responsiveness is important Can drain battery even when idle
Flicker: Refresh Power Reduction in DRAM Memories through Critical - - PowerPoint PPT Presentation
Flicker: Refresh Power Reduction in DRAM Memories through Critical - - PowerPoint PPT Presentation
Flicker: Refresh Power Reduction in DRAM Memories through Critical Data Partitioning Song Liu, Northwestern Univ. Karthik Pattabiraman, MSR Thomas Moscibroda, MSR Benjamin Zorn, MSR Motivation: Smart-phones Responsiveness is important
SLIDE 2
SLIDE 3
Motivation: DRAM Refresh
error rate power
refresh cycle [s]
64 mSec Where we are today Where we want to be X sec The
- pportunity
The cost If software is able to tolerate errors, we can lower refresh rates pretty drastically to save power
SLIDE 4
Flicker: Approach
- Critical / non-critical data partitioning
4
crit non-crit crit non-crit High refresh No errors Low refresh Some errors Flicker DRAM Important for application correctness e.g., pointers, key data structures Does not substantially impact app correctness e.g., multimedia data, soft state Mobile applications have substantial amounts of non-critical data
SLIDE 5
Flicker: Implementation
5
Programmer Allocator OS
High Refresh Rows Low Refresh Rows
Flicker DRAM critical object non-critical object critical page non-critical page virtual pages physical pages Minimal H/W changes: Variation of PASR DRAM
SLIDE 6
Flicker: Contributions
6
- First software technique to intentionally
lower hardware reliability for energy savings
- Minimal changes to hardware – based on
PASR mode in existing DRAMs
- No modifications required for legacy
applications – incremental deployment
- Reduced overall DRAM power by 20-25%
with negligible loss of performance ( < 1 %) and reliability across wide range of apps
SLIDE 7
The “Good Enough” Revolution
Source: WIRED Magazine (Sep 2009) – Robert Kapps http://www.wired.com/gadgets/miscellaneous/magazine/17-09/ff_goodenough