jm + latencies   5

Numbers Every Programmer Should Know, By Year
interactively explore how Jeff Dean's "Numbers Every Programmer Should Know" have changed over time (via Kishore Gopalakrishna)
memory  latency  hardware  history  jeff-dean  latencies  speed  performance 
4 weeks ago by jm
"Aeron: High-Performance Open Source Message Transport" [slides, PDF]
a new networked pub/sub library from Martin "Disruptor" Thompson, based around a replicated, persistent log of messages, with exceptionally low latency. Apache-licensed. Very similar to the realtime messaging stack we've built in Swrve. ;)
realtime  messaging  pub-sub  ipc  queues  transports  martin-thompson  slides  latencies  open-source  java  libraries 
november 2014 by jm
testing latency measurements using CTRL-Z
An excellent tip from Gil "HDRHistogram" Tene:
Good example of why I always "calibrate" latency tools with ^Z tests. If ^Z results don't make sense, don't use [the] tool. ^Z test math examples: If you ^Z for half the time, Max is obvious. [90th percentile] should be 80% of the ^Z stall time.
control-z  suspend  unix  testing  latencies  latency  measurement  percentiles  tips 
november 2014 by jm
Brownout: building more robust cloud applications
Applications can saturate – i.e. become unable to serve users in a timely manner. Some users may experience high latencies, while others may not receive any service at all. The authors argue that it is better to downgrade the user experience and continue serving a larger number of clients with reasonable latency.

"We define a cloud application as brownout compliant if it can gradually downgrade user experience to avoid saturation."

This is actually very reminiscent of circuit breakers, as described in Nygard’s ‘Release It!’ and popularized by Netflix. If you’re already designing with circuit breakers, you’ve probably got all the pieces you need to add brownout support to your application relatively easily.

"Our work borrows from the concept of brownout in electrical grids. Brownouts are an intentional voltage drop often used to prevent blackouts through load reduction in case of emergency. In such a situation, incandescent light bulbs dim, hence originating the term."
"To lower the maintenance effort, brownouts should be automatically triggered. This enables cloud applications to rapidly and robustly avoid saturation due to unexpected environmental changes, lowering the burden on human operators."

This is really similar to the Circuit Breaker pattern -- in fact it feels to me like a variation on that, driven by measured latencies of operations/requests.

See also .
circuit-breaker  patterns  brownout  robustness  reliability  load  latencies  degradation 
october 2014 by jm
Jeff Dean's list of "Numbers Everyone Should Know"
from a 2007 Google all-hands, the list of typical latency timings from ranging from an L1 cache reference (0.5 nanoseconds) to a CA->NL->CA IP round trip (150 milliseconds).
performance  latencies  google  jeff-dean  timing  caches  speed  network  zippy  disks  via:kellabyte 
march 2013 by jm

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