jm + timing   4

SolarCapture Packet Capture Software
Interesting product line -- I didn't know this existed, but it makes good sense as a "network flight recorder". Big in finance.
SolarCapture is powerful packet capture product family that can transform every server into a precision network monitoring device, increasing network visibility, network instrumentation, and performance analysis. SolarCapture products optimize network monitoring and security, while eliminating the need for specialized appliances, expensive adapters relying on exotic protocols, proprietary hardware, and dedicated networking equipment.

See also Corvil (based in Dublin!): 'I'm using a Corvil at the moment and it's awesome- nanosecond precision latency measurements on the wire.'

(via mechanical sympathy list)
corvil  timing  metrics  measurement  latency  network  solarcapture  packet-capture  financial  performance  security  network-monitoring 
may 2015 by jm
modern JVM concurrency primitives are broken if the system clock steps backwards
'The implementation of the concurrency primitive LockSupport.parkNanos(), the function that controls *every* concurrency primitive on the JVM, is flawed, and any NTP sync, or system time change, can potentially break it with unexpected results across the board when running a 64bit JVM on Linux 64bit.'

Basically, LockSupport.parkNanos() calls pthread_cond_timedwait() using a CLOCK_REALTIME instead of CLOCK_MONOTONIC. 'tinker step 0' in ntp.conf may be a viable workaround.
clocks  timing  ntp  slew  sync  step  pthreads  java  jvm  timers  clock_realtime  clock_monotonic 
september 2013 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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