## low latency – key expertise4GTD

I talked to a few big and small low-latency shops. I feel latency optimization is “low-logic, high speed, high throughput”. Below are the Expertise required, but in any real system, you will see diminishing return on each aspect, so remember to prioritize the cost-effective areas to optimize. See my post on 80/20 (http://bigblog.tanbin.com/2012/03/8020-rule-dimishing-return.html)

* threading
** parallel lock free threading but sometimes we can’t avoid inter-thread-comm (condVar)
** [L] try every technique to avoid locking (such as immmutables)

* [L] low-level memory management — custom allocators, custom (or disabled) garbage collectors
** care and feeding of java GC
** try every way to avoid non-deterministic garbage collection

* in-memory data stores — KDB etc
** This is how secDB compensates for some of the performance drawbacks
** state maintenance in memory — important in many OMS, DMA, exchange connectivity engines.

* try every techniques to avoid RDBMS
** use flat files

* low-latency messaging — 29West, tibrv messaging appliance …
** [H] async MOM is the only choice for high volume systems
** multicast is the de-facto standard

* OS monitoring and optimization
** dtrace
** network utilization
** paging activity
** cpu utilization

* [L] socket programming customized
* avoid ethernet collisions
* [H] avoid choke points, promote multi-lane highways
* [H] connectivity, collocation
* [L] serialization – customized
* [L] powerful hardware, FPGA
* [H] scale out – important
* 64 bit
* realtime java vs C++
[L] = low-level
[H] = high-level architectural feature

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