Hacker News: _wmd

New comment by _wmd in "Kernel analysis with bpftrace"

_wmd — Tue, 23 Jul 2019 10:08:25 +0000

The joy with bpftrace (and dtrace before it) for me is this ease with which 'synthetic' profiling events can be constructed from multiple underlying events. This can be used to, for example, only record the latency of malloc() while at least one TCP connection has been accepted and some particular function in your binary has already run at least once with its third parameter having a particular value

The offwake.bt example from the article is the closest to that, but it doesn't hook any userspace functions (like malloc). That's totally possible and extremely easy -- events can be mixed from wherever in the same script and, barring some knowledge like the fact the script is running on every CPU simultaneously, things just magically work

The main problem with bpftrace is that it's a pain in the ass to compile from source just now. A tool as useful as this really wants to be available on every machine by default

New comment by _wmd in "Inferno Operating System"

_wmd — Sun, 21 Jul 2019 01:07:20 +0000

I think the keyword here is transparency -- later designs (even stuff like MPI) explicitly expose the topology of the available hardware. SMP is the closest thing we've ever got to true transparency, and then only for 80% of cases, and for those only because the compute nodes have very similar locality and e.g. memory bandwidth

Even SMP requires careful control if you want to get anything close to the actual performance of the underlying hardware, and the topology is once again very explicit

New comment by _wmd in "Inferno Operating System"

_wmd — Sun, 21 Jul 2019 00:28:03 +0000

Transparently gluing boxes together over a low bandwidth fabric died as an active research area right around the time Plan9 was seeing its first development. By the late 80s shared bus SMP had demonstrated its practicality and quickly became the predominant architecture. Today we don't spawn processes on remote CPUs because the whole act of scheduling on multiple CPUs is entirely transparent to us, that's a competing architecture to the predecessor found in Plan 9

MOSIX is the only system from that era that I know is still around. It had a fork by the name of OpenMosix for some time, but according to Wikipedia ( https://en.wikipedia.org/wiki/MOSIX#openMosix ): "On July 15, 2007, Bar decided to end the openMosix project effective March 1, 2008, claiming that "the increasing power and availability of low cost multi-core processors is rapidly making single-system image (SSI) clustering less of a factor in computing"

(I admire the downvote, but please realize this is not a question of one's opinion!)

New comment by _wmd in "Windows 10 Debloat Script"

_wmd — Sat, 20 Jul 2019 21:10:36 +0000

If you can't answer this question for yourself, why do you think you'd be capable of modifying the factory default? Memory management is one of the most complex pieces of a modern OS

New comment by _wmd in "33 dead after arson attack at Kyoto Animation studio, dozens injured"

_wmd — Thu, 18 Jul 2019 11:12:39 +0000

The BBC article mentions many died on the stairs to the roof. Sounds like a locked door could have been involved

New comment by _wmd in "Issue: find a new home for repos including Requests"

_wmd — Wed, 17 Jul 2019 22:10:39 +0000

After the smear campaign and mass roasting he received less than 2 months ago, it's not hard to understand why any charitable intentions he had may have completely dried up

New comment by _wmd in "Declined Proposal: A built-in Go error check function, “try”"

_wmd — Wed, 17 Jul 2019 01:45:29 +0000

Python 2.1 or 2.2, sure

The EU Galileo GNSS has been down for 3 days

_wmd — Sun, 14 Jul 2019 20:55:30 +0000

Article URL: https://gsc-europa.eu/system-status/Constellation-Information

Comments URL: https://news.ycombinator.com/item?id=20435948

Points: 7

# Comments: 0

New comment by _wmd in "Details of the Cloudflare outage on July 2, 2019"

_wmd — Fri, 12 Jul 2019 17:50:53 +0000

So in response to a catastrophic failure due to testing in prod, they're going to push out a brand new regex engine with an ETA of 2 weeks. Can anyone say testing in prod?

The constant use of 'I' and 'me' (19 occurrences in total) deeply tarnishes this report, and repeatedly singling out a responsible engineer, nameless or not, is a failure in its own right. This was a collective failure, any individual identity is totally irrelevant. We're not looking for an account of your superman-like heroism, sprinting from meeting rooms or otherwise, we want to know whether anything has been learned in the 2 years since Cloudflare leaked heap all across the Internet without noticing, and the answer to that seems fantastically clear.

New comment by _wmd in "Linux Observability with BPF"

_wmd — Thu, 11 Jul 2019 17:25:18 +0000

hey! Do you know if anyone is working on getting bpftrace to use BTF yet? Looks like one of the final chunks landed in Linux 5.2

New comment by _wmd in "C. Hoare and Co., a British banking dynasty in business for more than 300 years"

_wmd — Tue, 09 Jul 2019 17:44:29 +0000

I'd imagine for a client, most of the value of this bank is access to what I can only imagine to be the most fantastically exotic network it sits at the centre of

New comment by _wmd in "Debian GNU/Hurd 2019 Released"

_wmd — Sun, 07 Jul 2019 14:03:15 +0000

There is quite a lot of surface area between a program and the kernel - C library, dynamic linker, system call interface, memory layout, droves of permission and sanity checking logic etc. that would need to be updated too. A 64 bit kernel is a first step

New comment by _wmd in "Raspberry Pi 4 not working with some chargers"

_wmd — Fri, 05 Jul 2019 13:02:02 +0000

Pretty unfortunate design flaw, and hopefully it can be corrected, but this post is horribly finger-pointy and the tone generally stinks. Would hate to make a mistake while working around this guy

Can the link be changed to the apparent source article? It's not as bad. https://www.scorpia.co.uk/2019/06/28/pi4-not-working-with-so...

New comment by _wmd in "Mailchimp to Sendy: Cutting Email Costs"

_wmd — Wed, 03 Jul 2019 16:10:47 +0000

DynamoDB's free tier is incredibly generous. Did you exceed it?

New comment by _wmd in "Cloudflare outage caused by bad software deploy"

_wmd — Tue, 02 Jul 2019 23:48:39 +0000

You'd think after leaking private data for literally months less than 3 years ago (and only noticing because Google had to point it out to them) that they'd, y'know, have at least some kind of QA environment fed with sample traffic by now. Really hard to believe they're still getting caught testing in prod

New comment by _wmd in "Google Cloud networking issues in us-east1"

_wmd — Tue, 02 Jul 2019 20:16:29 +0000

You can move 1.6TB between providers in a month for the same price as a single beefy DB server (m4.16xlarge here). That's a whole lot of logical replication..

New comment by _wmd in "Cloudflare Network Performance Issues"

_wmd — Tue, 02 Jul 2019 14:19:08 +0000

Centralizing more of the Internet to help people align their excuses is probably the worst reasoning I've ever read

New comment by _wmd in "PiHole-Google: Completely Block Google and Its Services"

_wmd — Sun, 30 Jun 2019 03:40:04 +0000

It's in SPF format, but it's also everything. See e.g. https://cloud.google.com/appengine/kb/

Another method is using GeoIP's ASN database, but they also run many ASNs so it would require a little effort to ensure you have them all

New comment by _wmd in "EC2 Instance Connect"

_wmd — Fri, 28 Jun 2019 11:29:08 +0000

Note the GCP equivalent requires some permanently running crapware inside your VM, the OpenSSH hook EC2 are using is much simpler

New comment by _wmd in "BTrDB: Berkeley Tree Database"

_wmd — Tue, 25 Jun 2019 23:52:52 +0000

https://www.usenix.org/system/files/conference/fast16/fast16...

Basic stats are recorded for the children of each tree node, and this is where the power-of-2 property comes from