cs4414 Fall 2013University of Virginia

David Evans

Class 15:Benchmarking

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Plan for Today

• Finish up Internet (from last class)• Midterm Discussion• Benchmarking

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Measuring NetworksLatency

Time from sending a bit until it arrives seconds (or seconds per geographic distance)

Bandwidth Rate at which can you transmitbits per second

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$ traceroute -q 1 -w 30 www.busselton.wa.gov.autraceroute to busselton.wa.gov.au (203.41.180.233), 64 hops max, 52 byte packets 1 dd-wrt (192.168.1.1) 11.156 ms 2 c-24-127-51-1.hsd1.va.comcast.net (24.127.51.1) 32.497 ms 3 te-2-3-ur01.charlville.va.richmond.comcast.net (68.85.226.149) 13.971 ms 4 xe-11-2-0-0-sur01.charlville.va.richmond.comcast.net (69.139.165.221) 12.312 ms 5 xe-4-1-2-0-ar02.charlvilleco.va.richmond.comcast.net (69.139.165.65) 12.395 ms 6 pos-1-2-0-0-cr01.ashburn.va.ibone.comcast.net (68.86.91.53) 25.624 ms 7 pos-3-10-0-0-cr01.56marietta.ga.ibone.comcast.net (68.86.86.221) 31.483 ms 8 pos-1-9-0-0-cr01.dallas.tx.ibone.comcast.net (68.86.87.233) 52.515 ms 9 he-0-12-0-0-cr01.losangeles.ca.ibone.comcast.net (68.86.86.117) 83.242 ms10 as4637-cr01.losangeles.ca.ibone.comcast.net (75.149.228.222) 78.134 ms11 i-0-2-0-11.tlot-core01.bi.telstraglobal.net (202.40.149.185) 86.131 ms12 i-0-0-0-0.sydo-core01.bx.telstraglobal.net (202.84.140.5) 287.302 ms13 tengige0-1-0-14.oxf-gw2.sydney.telstra.net (203.50.13.133) 300.060 ms14 bundle-ether2.oxf-gw1.sydney.telstra.net (203.50.6.85) 274.270 ms15 bundle-ether1.ken-core4.sydney.telstra.net (203.50.6.5) 270.694 ms16 bundle-ether10.win-core1.melbourne.telstra.net (203.50.11.13) 275.252 ms17 bundle-ether6.fli-core1.adelaide.telstra.net (203.50.11.90) 405.600 ms18 bundle-ether5.wel-core3.perth.telstra.net (203.50.11.19) 411.510 ms19 gigabitethernet0-1.wel13.perth.telstra.net (203.50.115.151) 406.044 ms20 *

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Does traceroute tell us anything about the bandwidth between here an Busselton, Austrailia?

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What Impacts Bandwidth?

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LAN: Ethernet (97.6% efficient for 12Kb packets)WAN: PPP (99.9% efficient – only 1-2 bytes overhead)

IPv4: up to 99.96% efficient

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Below all this: Physical Layer

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BandwidthHow much data can you transfer in a given amount of time?

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Improving Bandwidth

• Faster transmission– Train signalers to move semaphore flags faster– Use something less physically demanding to transmit

• Bigger pipes– Have multiple signalers transmit every other letter at the

same time

• Better encoding– Figure out how to code more than 98 symbols with

semaphore signal– Morse code (1840s)

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Morse CodeRepresent letters with series ofshort and long electrical pulses

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Circuit Switching

• Reserve a whole path through the network for the whole message transmission

Paris Toulon

Nantes

LyonBourges

Once you start a transmission,know you will have use of the network until it is finished. But,wastes network resources.

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Packet Switching

• Use one link at a time

Paris Toulon

Nantes

LyonBourges

Interleave messages – send whenever the next link is free.

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internetwork

A collection of multiple networks connected together, so messages can be transmitted between nodes on different networks.

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The First (international) internet

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1800: Edelcrantz links Sweden and Denmark telegraph networks to coordinate defense

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End of First (international) internet

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1801: British attach Copenhagen; Sweden doesn’t help Denmark; network disconnected

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The (capital-I) Internet

Packet Switching: Leonard Kleinrock (UCLA) thinks he did, Donald Davies and Paul Baran, Edelcrantz’s signalling network (1809)Internet Protocol: Vint Cerf, Bob KahnVision, Funding (DARPA): J.C.R. Licklider, Bob Taylor Government: Al Gore

First politician to promote Internet, 1986; act to connect government networks to form “Interagency Network”

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Vint Cerf (in the Rotunda, 2010)

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First Use of the Internet

October 1969: First packets on the ARPANet from UCLA to Stanford. Starts to send "LOGIN", but it crashes on the G.

How impressive is this compared to communications event 3 months earlier?

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20 July 1969:Live b/w video from the moon, transmitted

live to millions of televisions worldwide

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Today’s Internet: Bandwidth

Ethernet: up to 100 Mbits/sec

My office: ~50 M bits / sec

UVa Wireless: 57 M bits / sec

Cable modem at home:~ 30 M bits / sec

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projections

1 Petabyte = 1015 bytes1 Million petabytes = 1 zettabyte(NSA’s Utah facility is storing “Zbytes”?)

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Midterm Discussion

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Easiest Way to Ace Midterm

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4 people selected #9, but none were bold enough to leave all the other answers blank. (You should only be “especially proud of” your answer to #9 if you are confident enough to leave all other answers blank.)

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How many processes should a web browser create?

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1 process

several process

one per “tab”

several per “tab”

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How many threads should a web browser create?

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1 process

several process

one per “tab”

several per “tab”

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How many processes should a web browser developed in Rust

create?

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1 process

several process

one per “tab”

several per “tab”

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How many tasks should a web browser developed in Rust

create?

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1 process

several process

one per “tab”

several per “tab”

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Your technically unsophisticated (but smart, rich, and curious) uncle complains that his laptop is too noisy since the fan is running all the time. He expects that as someone taking upper-level computing courses at an elite, public university, you should be able to help him. What do you do?

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Hardware problem

or software problem?

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Hardware problem or

software problem?

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SOSP 2009

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Uncle’s Fan Problems

Could it be caused by deadlock?

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Fan Removes Heat

• CPU generates heat when it is executing lots of instructions

• At least with my MBP, one thread is not enough: 100% CPU usage – no fan200% CPU usage – light fan800% CPU usage – max fan

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PerformanceBenchmarking

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Why Benchmark?

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Developer Benchmarks

• Find bottlenecks: know what to spend time optimizing

• Measure impact of changes to optimize performance

• Predict what resources you will need to scale service (“healthcare.gov”)

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Goal is a benchmark that represents well the (anticipated) actual usage

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Micro vs. Macro Benchmarks

• Micro Benchmarks– Test one specific operation

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“Customer” Benchmarks

• Allow fair and accurate comparisons between different solutions

• Standard accepted by all/many vendors

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Goal is a benchmark that represents well the (anticipated) actual usage for “typical” users

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“Cheating” on Benchmarks

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How could you “cheat” on a benchmark?

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1. On the Exynos 5410, Samsung was detecting the presence of certain benchmarks and raising thermal limits (and thus max GPU frequency) in order to gain an edge on those benchmarks, and

2. On both Snapdragon 600 and Exynos 5410 SGS4 platforms, Samsung was detecting the presence of certain benchmarks and automatically driving CPU voltage/frequency to their highest state right away. Also on Snapdragon platforms, all cores are plugged in immediately upon benchmark detect.

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Everyone (except Google and NVidia) is cheating!

Samsung is just better at it than anyone else.

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Is It Possible to Prevent Benchmark “Cheating”?

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Benchmarking Zhtta

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http://www.comlore.com/redist_files/httperf-www2007-slides.pdf

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Example

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httperf --hog --server=localhost --port=4414 \ --num-conns=1000 --rate=10

10 requests per second

Should you run httperf on the machine running your server?

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Maximum connect burst length: 1

Total: connections 1000 requests 0 replies 0 test-duration 99.901 s

Connection rate: 10.0 conn/s (99.9 ms/conn, <=1 concurrent connections)Connection time [ms]: min 0.0 avg 0.0 max 0.0 median 0.0 stddev 0.0Connection time [ms]: connect 0.1Connection length [replies/conn]: 0.000

Request rate: 0.0 req/s (0.0 ms/req)Request size [B]: 0.0

Reply rate [replies/s]: min 0.0 avg 0.0 max 0.0 stddev 0.0 (19 samples)Reply time [ms]: response 0.0 transfer 0.0Reply size [B]: header 0.0 content 0.0 footer 0.0 (total 0.0)Reply status: 1xx=0 2xx=0 3xx=0 4xx=0 5xx=0

CPU time [s]: user 27.52 system 72.40 (user 27.6% system 72.5% total 100.0%)Net I/O: 0.0 KB/s (0.0*10^6 bps)

Errors: total 1000 client-timo 0 socket-timo 0 connrefused 1000 connreset 0Errors: fd-unavail 0 addrunavail 0 ftab-full 0 other 0

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Macrobenchmarks

Need a workload that represents typical load

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http://ita.ee.lbl.gov/html/traces.html

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http://www.hpl.hp.com/techreports/1999/HPL-1999-35R1.pdf

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1998Image from http://www.hpl.hp.com/techreports/1999/HPL-1999-35R1.pdf

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Macrobenchmarks

Need a workload that represents typical load

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Synthetic Workload Replayed Workload

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Weilin’s Test Workload

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> dd if=/dev/urandom of=5K.bin bs=5K count=1> dd if=/dev/urandom of=5M.bin bs=5M count=1> dd if=/dev/urandom of=10M.bin bs=10M count=1> dd if=/dev/urandom of=20M.bin bs=20M count=1> dd if=/dev/urandom of=40M.bin bs=40M count=1> dd if=/dev/urandom of=80M.bin bs=80M count=1> dd if=/dev/urandom of=512M.bin bs=512M count=1

http://www.cs.virginia.edu/~wx4ed/cs4414/ps3/zhtta-test-urls.txt

/5K.bin/index.htm/5K.bin/5K.bin/80M.bin/5K.bin/5K.bin/5K.bin/5K.bin/index.htm/5K.bin…

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Testing Zhtta

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> httperf --server localhost --port 4414 --rate 60 \ --num-conns 60 --wlog=y,./zhtta-test-urls.httperfTotal: connections 60 requests 60 replies 60 test-duration 32.588 s

Connection rate: 1.8 conn/s (543.1 ms/conn, <=46 concurrent connections)Connection time [ms]: min 0.4 avg 1237.8 max 31954.9 median 563.5 stddev 4132.5Connection time [ms]: connect 0.0Connection length [replies/conn]: 1.000

Request rate: 1.8 req/s (543.1 ms/req)Request size [B]: 67.0

Reply rate [replies/s]: min 0.0 avg 2.0 max 11.6 stddev 4.7 (6 samples)Reply time [ms]: response 1215.7 transfer 22.1Reply size [B]: header 71.0 content 16640936.0 footer 0.0 (total 16641007.0)Reply status: 1xx=0 2xx=60 3xx=0 4xx=0 5xx=0

CPU time [s]: user 7.40 system 25.12 (user 22.7% system 77.1% total 99.8%)Net I/O: 29920.6 KB/s (245.1*10^6 bps)

Errors: total 0 client-timo 0 socket-timo 0 connrefused 0 connreset 0Errors: fd-unavail 0 addrunavail 0 ftab-full 0 other 0

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Single-task server

Zhttpto

Zhtta with FIFO

Zhtta with SRPT

Zhtta with SRPT and caching

0 5 10 15 20 25 30 35 40

Test Total Duration (seconds)

Is our memory caching helping?

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Single-task server

Zhttpto

Zhtta with FIFO

Zhtta with SRPT

Zhtta with SRPT and caching

0 5000 10000 15000

Average Response Time (ms)

Single-task server

Zhttpto

Zhtta with FIFO

Zhtta with SRPT

Zhtta with SRPT and caching

0 5 10 15 20 25 30 35 40

Test Duration (seconds)

How good is this?

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Possible to do Much Better!

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Single-task server

Zhttpto

Zhtta with FIFO

Zhtta with SRPT

Zhtta with SRPT and caching

Apache2

0 5 10 15 20 25 30 35 40

Test Duration (seconds)

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Single-task server

Zhttpto

Zhtta with FIFO

Zhtta with SRPT

Zhtta with SRPT and caching

Apache2

0 2000 4000 6000 8000 10000 12000 14000 16000

Average Response Time (ms)

0.2 ms

httperf is measuring “Response Time” as latency to receive first byte!

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Charge

• You should definitely be able to show improvements using Weilin’s benchmark (posted with today’s notes)

• To prevent overly-targeted optimizing, we will also test your servers with a different workload

• Demo will separately check correctness– e.g., if a served file changes, should serve new file

not cached old one (within 10 seconds)– To prevent “cheating”, we may look at your code

17 October 2013

PS3 is due less than one week from today! Still, no one has claimed OpenPiazza!