Pinboard (jm)
https://pinboard.in/u:jm/public/
recent bookmarks from jmHow fast are Linux pipes anyway?2022-06-04T16:33:40+00:00
https://mazzo.li/posts/fast-pipes.html
jmkernel linux performance pipes vmsplice splice optimization syscalls unixhttps://pinboard.in/https://pinboard.in/u:jm/b:8390af0dda94/Missing Manuals - io_uring worker pool2022-02-09T11:53:13+00:00
https://blog.cloudflare.com/missing-manuals-io_uring-worker-pool/
jmlinux io_uring apis runtime kernel system-calls coding performancehttps://pinboard.in/https://pinboard.in/u:jm/b:14f82c98f81e/Orange-OpenSource/bmc-cache2021-09-20T09:14:30+00:00
https://github.com/Orange-OpenSource/bmc-cache
jmBMC (BPF Memory Cache) is an in-kernel cache for memcached. It enables runtime, crash-safe extension of the Linux kernel to process specific memcached requests before the execution of the standard network stack. BMC does not require modification of neither the Linux kernel nor the memcached application. Running memcached with BMC improves throughput by up to 18x compared to the vanilla memcached application.
]]>memcached bpf ebpf linux performance kernel via:brendangregghttps://pinboard.in/https://pinboard.in/u:jm/b:f4d6b7e18bd8/Boosting Dropbox upload speed—and making Windows’ TCP stack resilient to network reordering - Dropbox2021-05-18T22:04:37+00:00
https://dropbox.tech/infrastructure/boosting-dropbox-upload-speed
jmnetsh trace [...] correlates events on the wire with events that happen on the TCP layer, timers, buffer management, socket layer, and even the Windows asyncio subsystem (IOCP).
]]>windows tools cli networking dropbox iocp tcp ip internet kernelhttps://pinboard.in/https://pinboard.in/u:jm/b:9b45779da44f/TCP SACK PANIC - Kernel vulnerabilities - CVE-2019-11477, CVE-2019-11478 & CVE-2019-11479 - Red Hat Customer Portal2019-06-18T09:38:51+00:00
https://access.redhat.com/security/vulnerabilities/tcpsack
jmThree related flaws were found in the Linux kernel’s handling of TCP networking. The most severe vulnerability could allow a remote attacker to trigger a kernel panic in systems running the affected software and, as a result, impact the system’s availability.
The issues have been assigned multiple CVEs: CVE-2019-11477 is considered an Important severity, whereas CVE-2019-11478 and CVE-2019-11479 are considered a Moderate severity.
The first two are related to the Selective Acknowledgement (SACK) packets combined with Maximum Segment Size (MSS), the third solely with the Maximum Segment Size (MSS).
These issues are corrected either through applying mitigations or kernel patches. Mitigation details and links to RHSA advsories can be found on the RESOLVE tab of this article.
]]>tcp sack ip security vulnerabilities kernel bugshttps://pinboard.in/https://pinboard.in/u:jm/b:419ea005cabe/The log/event processing pipeline you can't have - apenwarr2019-02-18T00:19:49+00:00
https://apenwarr.ca/log/20190216
jmSimple things don't break. Our friends on the "let's use structured events to make metrics" team streamed those events straight into a database, and it broke all the time, because databases have configuration options and you inevitably set those options wrong, and it'll fall over under heavy load, and you won't find out until you're right in the middle of an emergency and you really want to see those logs. Or events.
]]>logging scalability klog kernel log-processing events embedded opshttps://pinboard.in/https://pinboard.in/u:jm/b:dbdd8c40549f/Over The Air - Vol. 2, Pt. 3: Exploiting The Wi-Fi Stack on Apple Devices2017-10-15T21:35:58+00:00
https://googleprojectzero.blogspot.ie/2017/10/over-air-vol-2-pt-3-exploiting-wi-fi.html
jm
Upon successful execution, the exploit exposes APIs to read and write the host’s physical memory directly over-the-air, by mapping in any requested address to the controlled DART L2 translation table, and issuing DMA accesses to the corresponding mapped IO-Space addresses.
]]>hacks exploits security ios wifi apple iphone kernelhttps://pinboard.in/https://pinboard.in/u:jm/b:84539adbb27c/awslabs/aws-ec2rescue-linux2017-07-21T09:54:23+00:00
https://github.com/awslabs/aws-ec2rescue-linux
jmAmazon Web Services Elastic Compute Cloud (EC2) Rescue for Linux is a python-based tool that allows for the automatic diagnosis of common problems found on EC2 Linux instances.
Most of the modules appear to be log-greppers looking for common kernel issues.
]]>ec2 aws kernel linux ec2rl opshttps://pinboard.in/https://pinboard.in/u:jm/b:1e8923ebc45e/Ubuntu on AWS gets serious performance boost with AWS-tuned kernel2017-04-11T10:54:52+00:00
https://insights.ubuntu.com/2017/04/05/ubuntu-on-aws-gets-serious-performance-boost-with-aws-tuned-kernel/?__s=gf36pf8g1gjugcqh6ppo
jmaws ubuntu ec2 kernel linux opshttps://pinboard.in/https://pinboard.in/u:jm/b:018d8e2ae296/Linux kernel bug delivers corrupt TCP/IP data to Mesos, Kubernetes, Docker containers — Vijay Pandurangan2016-04-28T09:36:03+00:00
https://tech.vijayp.ca/linux-kernel-bug-delivers-corrupt-tcp-ip-data-to-mesos-kubernetes-docker-containers-4986f88f7a19#.8pp079j3l
jmchecksums tcp veth ethernet drivers linux kernel bugs dockerhttps://pinboard.in/https://pinboard.in/u:jm/b:563365c76fe6/The revenge of the listening sockets2016-04-07T21:54:52+00:00
https://blog.cloudflare.com/revenge-listening-sockets/?p=0
jmYou can't have a very large number of bound TCP sockets and we learned that the hard way. We learned a bit about the Linux networking stack: the fact that LHTABLE is fixed size and is hashed by destination port only. Once again we showed a couple of powerful of System Tap scripts.
]]>ops linux networking tcp network lhtable kernelhttps://pinboard.in/https://pinboard.in/u:jm/b:4ba218682deb/The Nyquist theorem and limitations of sampling profilers today, with glimpses of tracing tools from the future2016-02-09T12:55:23+00:00
http://danluu.com/perf-tracing/
jmThe cause [of some mystery widespread 250ms hangs] was kernel throttling of the CPU for processes that went beyond their usage quota. To enforce the quota, the kernel puts all of the relevant threads to sleep until the next multiple of a quarter second. When the quarter-second hand of the clock rolls around, it wakes up all the threads, and if those threads are still using too much CPU, the threads get put back to sleep for another quarter second. The phase change out of this mode happens when, by happenstance, there aren’t too many requests in a quarter second interval and the kernel stops throttling the threads. After finding the cause, an engineer found that this was happening on 25% of disk servers at Google, for an average of half an hour a day, with periods of high latency as long as 23 hours. This had been happening for three years. Dick Sites says that fixing this bug paid for his salary for a decade. This is another bug where traditional sampling profilers would have had a hard time. The key insight was that the slowdowns were correlated and machine wide, which isn’t something you can see in a profile.
]]>debugging performance visualization instrumentation metrics dan-luu latency google dick-sites linux scheduler throttling kernel hangshttps://pinboard.in/https://pinboard.in/u:jm/b:670193c955f5/Linux futex_wait() bug2015-05-15T09:34:08+00:00
https://groups.google.com/forum/#!topic/mechanical-sympathy/QbmpZxp6C64
jmhaswell linux futex_wait futexes kernel bugs hanghttps://pinboard.in/https://pinboard.in/u:jm/b:51a581f19f79/The Discovery of Apache ZooKeeper's Poison Packet - PagerDuty2015-05-08T15:47:39+00:00
http://www.pagerduty.com/blog/the-discovery-of-apache-zookeepers-poison-packet/
jmzookeeper bugs error-handling bounds-checking oom poison-packets pagerduty packets tcpdump xen aes linux kernelhttps://pinboard.in/https://pinboard.in/u:jm/b:9374f1efc815/Linux kernel's Transparent Huge Pages feature causing 300ms-800ms pauses2014-11-04T18:05:19+00:00
https://groups.google.com/a/jclarity.com/forum/#!topic/friends/QPXl_8ce5Fg
jmredis memory defrag huge-pages linux kernel ops latency performance transparent-huge-pageshttps://pinboard.in/https://pinboard.in/u:jm/b:02aad4ff8ea8/BPF - the forgotten bytecode2014-05-23T13:25:17+00:00
http://blog.cloudflare.com/bpf-the-forgotten-bytecode
jmcoding dsl security via:oisin linux tcpdump bpf bsd kernel turing-complete configuration languageshttps://pinboard.in/https://pinboard.in/u:jm/b:b2414ac30ea5/Response to "Optimizing Linux Memory Management..."2013-10-23T16:28:35+00:00
http://kerneldave.blogspot.ie/2013/10/response-to-optimizing-linux-memory.html
jmDo not read in to this article too much, especially for trying to understand how the Linux VM or the kernel works. The authors misread the "global spinlock on the zone" source code and the interpretation in the article is dead wrong.
]]>linux tuning vm kernel linkedin memory numahttps://pinboard.in/https://pinboard.in/u:jm/b:028705973c7a/Rusty's API Design Manifesto2013-05-15T09:06:28+00:00
http://sweng.the-davies.net/Home/rustys-api-design-manifesto
jm
In the Linux Kernel community Rusty Russell came up with a API rating scheme to help us determine if our API is sensible, or not. It's a rating from -10 to 10, where 10 is perfect is -10 is hell. Unfortunately there are too many examples at the wrong end of the scale.
]]>rusty-russell quality coding kernel linux apis design code-reviews codehttps://pinboard.in/https://pinboard.in/u:jm/b:af2d8a163fb9/Microsoft's ill-chosen magic constants2012-07-16T12:38:45+00:00
http://mjg59.dreamwidth.org/14955.html
jmconstants via:kevin-lyda oh-dear microsoft fail magic-numbers boobs linux kernelhttps://pinboard.in/https://pinboard.in/u:jm/b:b63613157c8c/Ksplice » Solving problems with proc - System administration and software blog2011-01-11T21:28:45+00:00
http://blog.ksplice.com/2011/01/solving-problems-with-proc/
jmlinux sysadmin scripting kernel proc progress progress-bar pv hackshttps://pinboard.in/u:jm/b:0ef694a6a05f/Comparing genomes to computer operating systems in terms of the topology and evolution of their regulatory control networks — PNAS2010-05-06T10:00:34+00:00
http://www.pnas.org/content/early/2010/04/28/0914771107
jmvia:adulau papers toread genetics genome call-graph linux kernel e-coli operating-systems transcriptional-regulatory-networkhttps://pinboard.in/u:jm/b:eae2a1ce682d/KS2009: How Google uses Linux [LWN.net]2009-10-28T00:01:22+00:00
http://lwn.net/SubscriberLink/357658/1a5bf93645d9fe6e/
jmgoogle linux kernel open-source gpl free-softwarehttps://pinboard.in/u:jm/b:97213af22d6e/