Scalegrid

APRIL 23, 2021

Both Redis and Memcached are: NoSQL in-memory data structures Written in C Open source Used to speed up applications Support sub-millisecond latency In 2014, Salvatore wrote an excellent StackOverflow post on […]. Memcached, on the other hand, was created in 2003 by Brad Fitzpatrick.

Open Source 264

Open Source Latency C++ Speed 264

Brendan Gregg

JULY 2, 2021

biolatency Disk I/O latency histogram heat map. runqlat CPU scheduler latency heat map. Then, having discovered everything is C or Python, some rewrite it all in a different language. For a more recent example, I wrote cachestat(8) while on vacation in 2014 for use on the Netflix cloud, which was a mix of Linux 3.2

Latency 144

Latency Cache Energy Systems 144

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 103

Speed Java AWS Virtualization 103

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. Some people have found values that seem to work for their systems and workloads: they know that when load goes over X, application latency is high and customers start complaining.

Latency 111

Latency Metrics C++ Systems 111

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 78

Cache C++ AWS Java 78

ACM Sigarch

MARCH 18, 2019

How many buffers are needed to track pending requests as a function of needed bandwidth and expected latency? Can one both minimize latency and maximize throughput for unscheduled work? These models are useful for insight regarding the basic computer system performance metrics of latency and throughput (bandwidth). Little’s Law.

Systems 60

Systems Latency Performance Analytics 60

ACM Sigarch

MARCH 25, 2019

How many buffers are needed to track pending requests as a function of needed bandwidth and expected latency? Can one both minimize latency and maximize throughput for unscheduled work? The M/M/1 queue will show us a required trade-off among (a) allowing unscheduled task arrivals, (b) minimizing latency, and (c) maximizing throughput.

Systems 53

Systems Latency Performance C++ 53