Mike Meredith

Does Nobody Read RFC1918?

Oct 092018

And yes that includes me.

For those who don’t know, RFC1918 is the Internet standard that allocates the addresses used for private networks – 10/8, 192.168/16, or 172.16/12.

And in reference, specifically :-

To minimize the risk it is strongly recommended that an organization using private IP addresses choose randomly from the reserved pool of private addresses

(Apologies for the incorrect spelling above; it’s a quote from an American source)

This was reinforced to me yesterday whilst I was working from home, and I had trouble with a site-to-site VPN joining my network to work’s. As it happens there was no addressing conflict, but I had to install many routes more than should be necessary.

And I keep seeing this sort of thing; joining multiple networks when everybody is using 10/8 is a continual game of chicken – when are we going to find ourselves in conflict?

Of course there is a “fix” for this – NAT. The real fix of course is to use global IPv6 addresses even for devices and networks that will never be on the global Internet.

Optimising A Python Script

Computing, Working Notes No Responses »

Oct 032018

I have a Python script that over-simplifying, reads very large log files and runs a whole bunch of regular expressions on each line. As it had started running inconveniently slowly, I had a look at improving the performance.

The conventional wisdom is that if you are reading a file (or standard input), then the simplest method is probably almost always the fastest :-

for line in logstream:
    processline(line)

But being stubborn, I looked at possible improvements and came up with :-

from itertools import islice
    
while True:
    buffer = list(islice(logstream, islicecount))
    if buffer != []:
        for line in buffer:
             processline(line)
    else:
        break

This code has been updated twice because the first version added a splat to the output and the second version (which was far more elegant) didn’t work. The final version

This I benchmarked as being nearly 5% quicker – not bad, but nowhere near enough for my purposes.

The next step was to improve the regular expressions – I read somewhere that .* can be expensive and that [^\s]* was far quicker and often gave the same result. I replaced a number of .* occurrences in the “patterns” file and re-ran the benchmark to find (in a case with lots of regular expressions) the time had dropped nearly 25%.

The last step was to install nuitka to compile the Python script into a binary executable. This showed a further 25% drop – a script that started the day taking 15 minutes to run through one particular run ended the day taking just under 8 minutes.

The funny thing is that the optimisation that took the longest and had the biggest effect on the code showed the smallest improvement!

Steam on Linux

Computing, Linux No Responses »

Sep 102018

If you have not heard, Steam have added a compatibility layer to Steam which allows a limited number of Windows games to run. The “compatibility layer” is in fact a fork of WINE called Proton.

Peered at from 500 metres away, Proton allows Windows software to run (or not infrequently crash and burn) by translating the Win32 API into Linux APIs, and translating the variety of graphics APIs into Vulkan. That is a really difficult thing to do.

I have taken a very quick look at the new Steam client (and “Proton” is no longer part of a beta release of the Steam client – it’s in the standard client). It works perfectly adequately, although you will have variable experiences running Windows software.

For some reason this news has captured the imagination of a number of ‘tubers who are more gamers than Linux users, which has lead to some misunderstanding :-

This is not Linux gaming; it is Windows gaming under Linux. If you have a bad experience with Steam under Linux, you are not experiencing a bad time with Linux gaming. Linux gaming involves native Linux software, and yes there is some out there.
Problems with Steam could well be down to the Proton compatibility layer with unsupported API calls or buggy usage of the Win32 API which relies on Windows behaving in a certain way for undefined parameters.
In addition problems with Steam could be due to the hardware you are running; take a game that works perfectly fine with an Nvidia card. It may behave problematically with an AMD card or even a different Nvidia card. Or the other way around.

The important thing to remember when looking at videos about Steam is that the person looking at Steam may not be the most experienced Linux user out there. That is not necessarily bad – the whole purpose of Steam is to be able to run games easily without a whole lot of Linux experience.

But they may not be understanding properly what is going on – for example the first thing I would do as a professional game-orientated ‘tuber would be to try out a selection of games with an nvidia card, and then repeat using an AMD card – just to see if things work better, worse, or at least differently.

And again, this is not about Linux gaming but about allowing easy access to old Windows titles that someone may have bought in the past.

Linux: No You Don’t Need The Command-Line, But It Isn’t That Scary

Computing, Linux No Responses »

Sep 082018

Having used Linux for well over 20 years (yes it is that old), and Unix before that, I’m often puzzled by how scary some people seem to find Linux. Why should it be scary? It’s just a computer – you’re the human in charge of it.

Yes There Are Gooeys

(graphical user interfaces – GUIs – gooeys)

Yes there is plenty of software with a graphical user interface – I use plenty on a daily basis including a standard web browser, an email client, a password manager, an office package.

On a slightly less frequent basis there are many more that I use. Indeed providing that you accept the use of alternatives, you can find Linux software to do just about anything.

But Don’t Ignore The Command-Line

Yes, Linux has a command-line, and for those of us familiar with it, it can be very powerful. And there is no harm in learning how to use the command-line just to the point where you can follow instructions on how to “get something done” there.

Because if I have a fix for some niggle that you are having, it is easier and less error-prone to pass instructions for a command-line incantation than instructions for a gooey (and yes I have done both).

The Problematic PC Case

Computing No Responses »

Sep 062018

I recently put together a new PC (or mostly) and had occasion to look at what PC cases are like these days. In the end I kept my existing case, but did spend enough time looking to have certain opinions.

And they suck.

All about the glass windows to let the silly lights show through, but how about useful features?

Tool-less case panels? Or at least the top panel (to access the expansion cards).
Built-in cable runs so things (fans, SATA drives, etc) can be plugged in next to where they are installed.
On the subject of fans, servers often have easily removable fan trays; fans are mounted to a plastic frame which in turn slots into position together with power and control signals. A doddle to clean, which would be handy for a desktop workstation.
A front panel display to show fault messages during startup – firmware fault codes (some motherboards have a two-digit display but they’re optional and usually not visible when the case is closed). Post-boot it could be used for other things. If it breaks the clean lines of the case, put it behind a sliding panel or something.
Handles. And wheels.

There are probably a whole bunch more that could usefully be considered, and some of these are inherited from cases known to me (the old Mac Pro case is a good place to start from).

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