Brendan Gregg

SEPTEMBER 25, 2021

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. As (C) looked like a kernel rebuild, I started with (D) and (E). ## 5. Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? What on Earth is Ubuntu doing that results in 30% higher CPU time!?

Speed 126

Speed Java AWS Virtualization 126

Brendan Gregg

SEPTEMBER 25, 2021

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. As (C) looked like a kernel rebuild, I started with (D) and (E). Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? What on Earth is Ubuntu doing that results in 30% higher CPU time!?

Speed 52

Speed Java AWS Virtualization 52

Brendan Gregg

SEPTEMBER 25, 2021

A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. As (C) looked like a kernel rebuild, I started with (D) and (E). ## 6. Measuring the speed of time Is there already a microbenchmark for os::javaTimeMillis()? What on Earth is Ubuntu doing that results in 30% higher CPU time!?

Speed 40

Speed Java AWS Virtualization 40

Brendan Gregg

MAY 8, 2021

Update: Some modern drives after 2015 are sealed with [helium].) It seemed to have several set speeds, and when pushing hard it would try a faster speed for a couple of seconds, then a faster one, until it found the fastest it could operate (presumably it tries faster speeds until it begins to get sector-ECC errors).

Performance 40

Performance Latency Speed Systems 40

Brendan Gregg

AUGUST 8, 2017

TABLE OF EXP(-T/C) FOR T = 5 SEC. EXPFF: EXP 0.920043902 ;C = 1 MIN EXP 0.983471344 ;C = 5 MIN EXP 0.994459811 ;C = 15 MIN. Anyway, the following patch seems to make the load average much more consistent WRT the subjective speed of the system. Latency was acceptable and no one complained.

Latency 111

Latency Metrics C++ Systems 111

Smashing Magazine

JANUARY 6, 2020

You need a business stakeholder buy-in, and to get it, you need to establish a case study, or a proof of concept using the Performance API on how speed benefits metrics and Key Performance Indicators ( KPIs ) they care about. Start Render time, Speed Index ). Treo Sites provides competitive analysis based on real-world data.

Performance 145

Performance Cache Network Metrics 145

Smashing Magazine

JANUARY 7, 2019

You need a business stakeholder buy-in, and to get it, you need to establish a case study on how speed benefits metrics and Key Performance Indicators ( KPIs ) they care about. Note : If you use Page Speed Insights (no, it isn’t deprecated), you can get CrUX performance data for specific pages instead of just the aggregates.

Performance 103

Performance Cache Metrics Network 103