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. We'll likely open source the new one at some point and have a post about it on the Netflix tech blog. ## Case study: Facebook Facebook are advanced users of BPF, but deep details of how they run the tools fleet-wide aren't fully public.

Latency 145

Latency Cache Energy Systems 145

Brendan Gregg

AUGUST 29, 2021

biolatency From [bcc], this eBPF tool shows a latency histogram of disk I/O. Hit Ctrl-C to end. ^C C msecs : count distribution 0 -> 1 : 83 | | 2 -> 3 : 20 | | 4 -> 7 : 0 | | 8 -> 15 : 41 | | 16 -> 31 : 1620 | * | 32 -> 63 : 8139 | *| 64 -> 127 : 176 | | 128 -> 255 : 95 | | 256 -> 511 : 61 | | 512 -> 1023 : 93 | |. 41 33681 ^C.

Cache 105

Cache C++ AWS Latency 105

ACM Sigarch

MARCH 25, 2019

With two blog posts, we argue for more use of simple models beyond Amdahl’s Law. Previously, Part 1 of these two blog posts provided our thesis that analytic models can complement measurement and simulations to give quick insight, show what is not possible, provide a double-check, and suggest future directions. and 1/S as ?.

Systems 53

Systems Latency Performance C++ 53

ACM Sigarch

MARCH 18, 2019

With two blog posts, we argue for more use of simple models beyond Amdahl’s Law. To this end, we present three simple models that we find useful like Amdahl’s Law, split here into two blog posts. How many buffers are needed to track pending requests as a function of needed bandwidth and expected latency? Answered in Part 2.).

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

AUGUST 29, 2021

100.00 ^C I'm looking at the r_await column in particular: the average wait time for reads in milliseconds. biolatency From [bcc], this eBPF tool shows a latency histogram of disk I/O. Hit Ctrl-C to end. ^C Hit Ctrl-C to end. ^C avg-cpu: %user %nice %system %iowait %steal %idle 14.81 I think it's the workload. ## 4.

Cache 40

Cache C++ AWS Systems 40