Brendan Gregg

SEPTEMBER 25, 2021

These strange questions came to the fore back in 2014 when Netflix was switching services from CentOS Linux to Ubuntu, and I helped debug several weird performance issues including one I'll describe here. A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. How would you _time_ time?

Speed 126

Speed Java AWS Virtualization 126

Brendan Gregg

JULY 2, 2021

biolatency Disk I/O latency histogram heat map. runqlat CPU scheduler latency heat map. This is thinking like a sysadmin who installs and maintains software, and not like a programmer who codes everything. Then, having discovered everything is C or Python, some rewrite it all in a different language. BPF up and running!

Latency 145

Latency Cache Energy Systems 145

Brendan Gregg

SEPTEMBER 25, 2021

These strange questions came to the fore back in 2014 when Netflix was switching services from CentOS Linux to Ubuntu, and I helped debug several weird performance issues including one I'll describe here. A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. How would you time time?

Speed 52

Speed Java AWS Virtualization 52

ACM Sigarch

MARCH 18, 2019

Existing systems can be studied with measurement, while prospective systems are most often studied by extrapolating from measurements of prior systems or via simulation software that mimics target system function and provides performance metrics. Can one both minimize latency and maximize throughput for unscheduled work? Little’s Law.

Systems 60

Systems Latency Performance Analytics 60

Brendan Gregg

SEPTEMBER 25, 2021

These strange questions came to the fore back in 2014 when Netflix was switching services from CentOS Linux to Ubuntu, and I helped debug several weird performance issues including one I'll describe here. A Cassandra database cluster had switched to Ubuntu and noticed write latency increased by over 30%. How would you _time_ time?

Speed 40

Speed Java AWS Virtualization 40

Brendan Gregg

JULY 2, 2021

biolatency Disk I/O latency histogram heat map 5. runqlat CPU scheduler latency heat map 10. They need constant updates to keep working across different software versions. As an extreme example, I wrote cachestat(8) while on vacation in 2014 for use on the Netflix cloud, which was a mix of Linux 3.2 patch to Linux 5.12.

Open Source 40

Open Source Latency Cache Energy 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. I generated this using my offcputime tool from [bcc] (this tool needs eBPF features from Linux 4.8+), and my [flame graph] software: #./bcc/tools/offcputime.py Yes, I'd say so.

Latency 111

Latency Metrics C++ Systems 111