Month: November 2014
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The delights and frustrations of assembly programming
They say of C it has all the speed of assembly programming and all the maintainability of … assembly programming. What it lacks is the basic sense of complete mastery over the machine that a successful piece of assembly delivers but, actually, it is a bit easier to maintain than assembly. These past few weeks, […]
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A timerless CLOCK algorithm
I am writing this down partly as a way of seeing if it makes sense… Minor faults we can live with: if we have to reaffix a mapping back into the TLB it takes a few cycles but that is not a heavy burden. Major faults, however, are a different matter: they take many thousands […]
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Picking which page to remove
I have now written some very basic but functional paging code for the Microblaze but have realised I am, essentially, going to have to start a lot of it again. The Microblaze puts page tables firmly under software control and its memory management unit (MMU) concentrates on managing page references through its translation lookaside buffers […]
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Why I owe @slugonamission a (or several) large drink(s)
I have been struggling with a problem with my Microblaze simulation on OVPsim all week. I have been trying to make a start on implementing a simple demand paging system and to trigger the hardware exception that the Microblaze CPU manual says should happen when you either try to read from a mapped page that […]
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Referenced in an academic text book
My MSc project on memory management in the Linux kernel has indeed been referenced in an academic text book – Computing Handbook, Third Edition: Computer Science and Software Engineering – you can look me up in the preview there. The article that references my work is by the great Peter J. Denning, the “father” of […]
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Latest Microblaze puzzle
Having successfully written a couple of simple virtual memory mappings I now want to write the exception handling code that will allow me to swap mappings in and out – so I did this: I expected that the marked line would raise a hardware exception as a TLB miss and I’d be taken to the […]
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Computer programming centre-right lovers of Swedish meatballs
According to YouGov (the UK’s largest polling company) that is what typical lovers of Linux are – though it’s based on just 272 individual profiles (out of 200,000 or so members of YouGov’s panel). Oh, and they are blokes. More at https://yougov.co.uk/profiler#/Linux/demographics (YouGov made at least some of their profiling data available online this morning […]
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The Imitation Game
The first things to say about this film is that it is well worth seeing, profoundly moving and (in general) very well acted. The second is that it gets to be this way by rather playing with the facts. #520714001 / gettyimages.com I am no Turing expert – I’ve read On Computable Numbers (via the […]
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Of course turning on the MMU breaks your code!
Tonight I finally managed to get the code and the sequencing right to not just boot the Microblaze simulation, but to turn on the MMU. But I was puzzled as to why, as soon as I had done that, the execution breaks with a segmentation fault and appeared to be executing code I had not […]
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First working assembly code in 33 years
When I say working, I mean boots into an endless loop with no ouput to the user – but then, that’s what it’s meant to do: Only have to get it to do something useful now, how hard could that be? (There is a linker script to get this to work also – as it […]
cartesian product ... stuff about computing mostly 