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. I also rewrote this in C and called gettimeofday(2) directly: $ cat gettimeofdaybench.c. 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). I also rewrote this in C and called gettimeofday(2) directly: $ cat gettimeofdaybench.c 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. I also rewrote this in C and called gettimeofday(2) directly: $ cat gettimeofdaybench.c What on Earth is Ubuntu doing that results in 30% higher CPU time!?

Speed 40

Speed Java AWS Virtualization 40

Smashing Magazine

JANUARY 6, 2020

Estimated Input Latency tells us if we are hitting that threshold, and ideally, it should be below 50ms. Designed for the modern web, it responds to actual congestion, rather than packet loss like TCP does, it is significantly faster , with higher throughput and lower latency — and the algorithm works differently.

Performance 145

Performance Cache Network Metrics 145

Smashing Magazine

JANUARY 11, 2021

Estimated Input Latency tells us if we are hitting that threshold, and ideally, it should be below 50ms. Designed for the modern web, it responds to actual congestion, rather than packet loss like TCP does, it is significantly faster , with higher throughput and lower latency — and the algorithm works differently.

Performance 145

Performance Cache Media Metrics 145