Viewing profile — andikleen2

Dave Jones used to have a series of "Why user space sucks" Linux kernel conference talks with many such examples, usually with dumb and redundant system calls. However as someone w…

Early x86-64 Linux had a similar problem. The x86-64 ABI uses registers for the first 6 arguments. To support variable number of arguments (like printf) requires passing the number…

If you read Anderson "A history of Aerodynamics" it disagrees on this point. It states that the Wright's didn't have a good way to calculate drag, and they didn't understand many o…

> 4. First design that used a wind tunnel to get an efficient wing shape The Wrights based their wing on Lilienthal's who used a variant of a wind tunnel (as well as actual gliders…

This technique works with any instruction that clobbers a register, not just with CPUID. In the worst case you could just single step the other CPUs until you hit an instruction th…

Having spent a lot of time porting 32bit system code to 64bit, I developed a dislike for these explicit types. It's a slippery slope to hard code your bitness with people making as…

Back when Usenet was still functional, de.sci.history (German history group) had some dedicated proponents of a German conspiracy theory that the early middle ages (Carolingian dyn…

Even if they don't livelock retries can be significantly slower than a direct atomic operation under contention. Compare https://www.cs.tau.ac.il/~mad/publications/ppopp2013-x86que…

>Put simply, TSX is not mainstream, and isn't on track to be mainstream anytime soon. Being in the vast majority of servers deployed in the last decade (Intel+POWER) is not mainstr…

Yes it totally is. How much confidence do you have in your lockless code?

>essentially no cost unless the lock is contested. Atomics are not free. And fetching a cache line can be very expensive, even without contention. However lock less algorithms are …

In the early tens we ran an engineering project to improve critical sections in applications using transactional memory. We had a PhD level intern applying our techniques to variou…

Seems trivial to exploit the kernel module: struct network_activity * activity = NLMSG_DATA(nlh); append_rule(activity->process_path, (activity->allowed == 1)); ... append_rule: //…

Small mistake in the article. System V code was never released publicly by SCO, just some earlier variants not too far removed from V7. They make great code reading if anyone is in…

You have to be a bit careful with the CLFLUSH method. I tried to use it in a widely used program years ago because Intel recommended it, but we found that it just hangs the CPU on …

Yes with a read primitive it could be done in theory. It will be just quite awkward to use however as every caller has to do all that: define a lock, pass it always in, make sure t…

This would be only useful for "good" page faults that fault something in, but not for "bad" ones (like NULL pointer). If a bad page fault was executed it would allow transactions t…

Practically all valid fallback schemes require putting the lock (or something else like a sequence counter for a STM) into the read set of the transaction to properly synchronize b…

He's assuming that retrying forever is a valid retry strategy, which it is not. For example if a page fault was needed to satisfy one of the memory access it would never finish. Se…