Hacker News Reader

_wmdon Kernel analysis with bpftrace

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

_wmdon Inferno Operating System

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

_wmdon Inferno Operating System

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!)

_wmdon Windows 10 Debloat Script

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

_wmdon 33 dead after arson attack at Kyoto Animation studio, dozens injured

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

_wmdon Issue: find a new home for repos including Requests

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

_wmdon Declined Proposal: A built-in Go error check function, “try”

Python 2.1 or 2.2, sure

_wmdon Details of the Cloudflare outage on July 2, 2019

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.

_wmdon Linux Observability with BPF

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

_wmdon C. Hoare and Co., a British banking dynasty in business for more than 300 years

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

_wmdon Debian GNU/Hurd 2019 Released

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

_wmdon Raspberry Pi 4 not working with some chargers

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...

_wmdon Mailchimp to Sendy: Cutting Email Costs

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

_wmdon Cloudflare outage caused by bad software deploy

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

_wmdon Google Cloud networking issues in us-east1

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..

_wmdon Cloudflare Network Performance Issues

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

_wmdon PiHole-Google: Completely Block Google and Its Services

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

_wmdon EC2 Instance Connect

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

_wmdon BTrDB: Berkeley Tree Database

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

_wmdon Query Plan Caching in CockroachDB

It's certainly a name you can't forget easily, but there's nothing dumb about it. It's intended to be a highly survivable system, that's where the name came from -- in popular culture cockroaches are supposed to be able to survive a nuclear attack. It's a great connotation

_wmdon Cloudflare Time Services

While I think your conclusion is a little strong, it is fair to say they're trying their hardest to legitimize by becoming entangled into almost every possible piece of infrastructure around.

As far as giant databases in the sky are concerned, in my book Cloudflare joined the same category as Google a long time ago. I don't like them because they've become another data-aggregating SPOF anyone with sense should actively avoid depending on

_wmdon Firefox zero-day was used in attack against Coinbase employees, not its users

You almost make it sound like Chrome weren't written in C++, or that the typical Chrome install weren't hosted on a few 10s of millions of lines of C/C++

_wmdon Google Researcher Publishes Windows 10 Zero-Day Security Vulnerability

I've been around infosec for 21 years and this is still a 0day. That term has no strong definition, certainly not one that would allow precise interpretation as above, but in this case even a vague sense of what it means covers the situation easily: _users_ have had no time to patch

_wmdon Project Galileo: five years of protecting the vulnerable online

> He followed our run book and triggered a FINT — which stands for "Fail Internal" — directing traffic from the site directly back to its origin rather than passing through Cloudflare's protective edge. Instantly the site was overwhelmed by the attack and, effectively, fell off the Internet.

So if I'm understanding this correctly, free users have their backend servers and hosting provider information exposed to an attacker right when that information needs to be kept secret the most? This is nuts. Can someone clarify whether CloudFlare still do this? I can think of 100 scenarios where it would be better to just pull the zone (or similar) and let the site go down instead

_wmdon Ask HN: Does anyone still use IRC?

While Freenode may not compete with Facebook, it's still pretty huge :)

    There are 99 users and 84066 invisible on 32 servers
    36 IRC Operators online
    16 unknown connection(s)
    53438 channels formed 
    I have 5185 clients and 1 servers
    5185 5972 Current local users 5185, max 5972
    84165 94773 Current global users 84165, max 94773
    Highest connection count: 5973 (5972 clients) (476397 connections received)

_wmdon A novel data-compression technique for faster computer programs

Paper: https://people.csail.mit.edu/poantsai/papers/2019.zippads.as...

Seems this cannot be read without first understanding "object based memory hierarchies", which is new to me. This coauthor's page has a ton of related papers: http://people.csail.mit.edu/poantsai/

_wmdon Has the Python GIL Been Slain? Subinterpreters in Python 3.8

Considering this will require basically a total rewrite of the C extension API, without having had a chance to look yet, the idea it could be done in a minor release seems shocking

_wmdon Has the Python GIL Been Slain? Subinterpreters in Python 3.8

Whoever is downvoting this, please realize this design stinks strongly of something Perl5 had a long time ago, that almost nothing could make use of due to a variety of limitations.

The question in my mind is how the Python design addresses the problems that made the perl equivalent so unusable. It's only had ~20 years of context to do better, so I'm hopeful

_wmdon The New Windows Subsystem for Linux (WSL2) Architecture [video]

This is fairly classic engineer thinking and what I was referring to in my comment below.. you can wrap a GPL library in its own program, put that program on a separate VM on a separate physical host in a separate physical building, talk to it only over a network interface and your program's resulting interaction with it might still be construed as linking.

Similarly, your program might statically link against a GPL'd library, but only pass bulk data through a programming interface in a coarse manner, and the result may not be considered linking. The FSF FAQ even explicitly addresses this case.

GPL leaves these kinds of mechanisms blurry and ill-defined (I presume intentionally), it's just that as engineers we are commonly only taught how violations manifest in the usual case.

_wmdon The New Windows Subsystem for Linux (WSL2) Architecture [video]

The interpretation around what "linking" means in the context of the GPL is a full-time job. At the least, the literal interpretation I was raised with has never been the official position of the FSF. For example, just because you link a library statically doesn't mean you're GPL-violating. You need to for example, swap complex data structures in some complex control flow to cross the line.

Even then there are still more exceptions for 'runtimes' and suchlike where while in a literal sense, the final assembled program when executing is linked against GPL source the result is not considered to be covered by the GPL.

None of this stuff is actually part of the license text -- it's built on precedence and common understanding. These things are a lawyer's job, we're just engineers