jm + xen   5

The Discovery of Apache ZooKeeper's Poison Packet - PagerDuty
Excellent deep dive into a production issue. Root causes: crappy error handling code in Zookeeper; lack of bounds checking in ZK; and a nasty kernel bug.
zookeeper  bugs  error-handling  bounds-checking  oom  poison-packets  pagerduty  packets  tcpdump  xen  aes  linux  kernel 
may 2015 by jm
What Color Is Your Xen?
What a mess.
What's faster: PV, HVM, HVM with PV drivers, PVHVM, or PVH? Cloud computing providers using Xen can offer different virtualization "modes", based on paravirtualization (PV), hardware virtual machine (HVM), or a hybrid of them. As a customer, you may be required to choose one of these. So, which one?
ec2  linux  performance  aws  ops  pv  hvm  xen  virtualization 
february 2015 by jm
Testing fork time on AWS/Xen infrastructure
Redis uses forking to perform persistence flushes, which means that once every 30 minutes it performs like crap (and kills the 99th percentile latency). Given this, various Redis people have been benchmarking fork() times on various Xen platforms, since Xen has a crappy fork() implementation
fork  xen  redis  bugs  performance  latency  p99 
october 2014 by jm
'Bobtail: Avoiding Long Tails in the Cloud' [pdf]
'A system that proactively detects and avoids bad neighbouring VMs without significantly penalizing node instantiation [in EC2]. With Bobtail, common [datacenter] communication patterns benefit from reductions of up to 40% in 99.9th percentile response times.'

Excellent stuff -- another conclusion they come to is that it's not the network's fault, it's the Xen hosts themselves. The EC2 networking team will be happy about that ;)
networking  ec2  bobtail  latency  long-tail  xen  performance 
february 2014 by jm

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