Somniloquy*: Augmenting Network Interfaces to Reduce PC Energy Usage Ranveer Chandra (Microsoft Research) Yuvraj Agarwal, Rajesh Gupta (UCSD), Victor Bahl, Steve Hodges, James Scott (MSR) *som-nilo-quy (noun): The act or habit of talking while asleep.

Context: IT Power Use Is Large Studies show that: – 67% of office PCs powered up after work hours “Sleep” modes used in <4% ! [1] – Home PCs are left on for 34% of the time 50% of the time they are not being used Confirmed by our measurements: – UCSD: 600+ desktops left ON (total each  ~100kW (25% of total energy) Energy Cost: $9/Hr or $200/day ! [1] J. Roberson et al. “After-hours Power Status of Office Equipment and Energy use of Miscellaneous Plug-load Equipment. Lawrence Berkeley National Laboratory, Berkeley, California. Report# LBNL Revised,

Motivating survey Motivating survey of 107 computer users Respondents regularly left 75% of office PCs and 30% of home PCs on unattended Popular apps left running included file sharing, /IM, remote desktop login and remote file sharing What apps do you leave running on your computer? 3

Saving Power Runs into Usability Why do people leave their PCs on? – Maintain desktop, applications left open Can be handled by low-power modes (Sleep, Hibernate) – Occasional access Remote Desktop, file sharing Administrative: updates, patches, backups – Active applications running Maintaining presence: e.g. incoming Skype call, IM Long running applications: Web downloads, BitTorrent 4

Power Management vs. Use Models Current design trends: – Hosts (PCs): either Awake (Active) or Sleep (Inactive) Power consumed when Awake = 100X power in Sleep! – Network: Assumes hosts are always “Connected” (Awake) What users really want: – Provide some functionality of an Awake (active) host… ….While consuming power in Sleep mode? – Resume host to Awake mode only if needed Change the fundamental distinction between Sleep and Active states… 5

Somniloquy*: PCs that talk in their sleep Somniloquy daemon Somniloquy daemon Host processor, RAM, peripherals, etc. Operating system, including networking stack Apps Network interface hardware Secondary processor Embedded CPU, RAM, flash Embedded OS, incl. networking stack wakeup filters Appln stubs Host PC Augment network interfaces: – Add a separate power domain ON when host is asleep Processor + Memory + Storage + Network stack – Same MAC/IP Address – Transparent to network, remote hosts and servers Wake-up Host when needed – E.g. Incoming Connection Handle some applications when PC remains asleep – Using “application stubs” *som-nilo-quy (noun): The act or habit of talking while asleep. 6

Somniloquy Prototype Prototype uses “gumstix” platform – PXA270 processor with full TCP/IP stack – USB connection to PC for sleep detection/wakeup trigger, power whilst asleep, and IP networking for data Wired and Wireless versions 1NIC version follows initial vision of augmented NIC, where all data goes via gumstix even when PC is awake 2NIC version uses PC’s internal interface while it is awake, and allows for simpler legacy-friendly support Wired-1NIC prototype Wireless-2NIC prototype 7

USB Interface (Wakeup Host + Status + Debug) USB Interface (power + USBNet) 100Mbps Ethernet Interface Processor SD Storage Prototype 8

Somniloquy in Operation (1) Maintain reachability – “ping”, ARP queries, maintain DHCP Desktop going to Sleep 4 seconds Desktop resuming from Sleep 5 seconds 9

Somniloquy in Operation (2) Wake-up host on any user defined “filter” – E.g. incoming VoIP call, RDP request Specified at any layer of the network stack – E.g. from a particular IP (layer-3) or MAC (layer-2) Measured “user perceived” increase in latency – 3s – 10s across all tested applications – E.g. VoIP call takes 8 seconds vs 4 seconds to set up 10

“Setup” latency for our prototypes Measured time till user-perceived response for RDP, SMB and VOIP For each, incoming TCP SYN caused wakeup Additional latency ranges from 3-10s for all prototype versions As a proportion of the resulting computing session, this is OK 11

What about active applications ? P2P file sharing (BitTorrent), background downloads, maintaining IM presence Need application specific code on the NIC – Limited processing, storage ? – Cannot run the full application Offload part of the applications: i.e. “stub” code – Generate “stub” code manually (for now..) 12

Somniloquy in Operation: Web download Stub Run web download “stub” on the gumstix – 2GB SD storage, download when PC is asleep – Wake-up PC and upload to PC when needed – 92% less energy than using the host PC for download! 13

Power Savings Our gumstix prototype: – Draws 250mW (idle) to 1.6W (network flood) Test Desktop, – Power drops from >100W to <5W, i.e. 620kWh saved per year (US$56, 378 kg CO 2 ) Test Laptop, – Power drops from >11W to ~1W, battery life increases from 60 hours Dell Optiplex 745 Power Consumption 14

Summary Somniloquy: Augments NICs – Network connected while PC is asleep Enables Energy savings: – Millions of office PCs (e.g. for RDP, File sharing, updates – Home PCs (e.g. P2P file shares, media centers) Savings of ~100W per desktop! 15

Current Work: Enterprise environments: – Adding hardware to desktop PCs costly – Enterprises: management, maintenance costs Somniloquy without adding hardware ? – Yes - It’s possible! – However, need some help from the network – Stubs : Can we generate them automatically ? Home desktops/Laptops: Somniloquy still needed 16

Thank you! Questions ? 17

Backup Slides 18

Somniloquy*: PCs that talk in their sleep Augment network interfaces such that: – Add a separate power domain ON when host is asleep Processor + Memory + Storage + Network stack – Masquerade as the host itself Transparent to: – End hosts and applications – Network infrastructure – Remote servers *som-nilo-quy (noun): The act or habit of talking while asleep. Wired prototype Wireless prototype 19

Current Work (2): Instrumenting CSE: – Detailed power monitoring! – JIGSAW except for power – How much is HVAC power? Desktops? – How much can we reduce? 20

Wake-on-LAN - Why it doesn’t work Requires BIOS/Operating System support Requires router infrastructure support – Cannot go across subnets, (subnet broadcast) Granularity is very coarse – Too few or too many wakeups Very limited in functionality – Cannot handle application stubs 21