Largely, for the same reason you start at the least significant digit (the right end) when you add—because carries propagate toward the more significant digits. Putting the least significant byte first allows the processor to get started on the add after having read only the first byte of an offset. After you’ve done enough assembly … Read more
First method – Easiest option- Check your Task Manager If you have Windows 10 or Windows 8 operating system, the easiest way to check is by opening up Task Manager->Performance Tab. You should see Virtualization as shown in the below screenshot. If it is enabled, it means that your CPU supports Virtualization and is currently … Read more
How to distinguish between high- and low-performance cores/threads in C++? Please understand that “thread” is an abstraction of the hardware’s capabilities and that something beyond your control (the OS, the kernel’s scheduler) is responsible for creating and managing this abstraction. “Importance” and performance hints are part of that abstraction (typically presented in the form of … Read more
Just imagine, how the processor would execute a typical spin-wait loop: 1 Spin_Lock: 2 CMP lockvar, 0 ; Check if lock is free 3 JE Get_Lock 4 JMP Spin_Lock 5 Get_Lock: After a few iterations the branch predictor will predict that the conditional branch (3) will never be taken and the pipeline will fill with … Read more
As noted below by @thakis, newer versions of Clang (3.5+) accept the -masm=intel argument. For older versions, this should get clang to emit assembly code with Intel syntax: clang++ -S -mllvm –x86-asm-syntax=intel test.cpp You can use -mllvm <arg> to pass in llvm options from the clang command line. Sadly this option doesn’t appear to be … Read more
There isn’t a single “intel CPU”, especially in terms of what operations are optimized with respect to others!, but most of them, at CPU level (specifically within the FPU), are such that the answer to your question: are double operations just as fast or faster than float operations for +, -, *, and /? is … Read more
This is commonly caused by running out of file descriptors. There is the systems total file descriptor limit, what do you get from the command: sysctl fs.file-nr This returns counts of file descriptors: <in_use> <unused_but_allocated> <maximum> To find out what a users file descriptor limit is run the commands: sudo su – <username> ulimit -Hn … Read more
In older times, microcode was heavily used in CPU: every single instruction was split into microcode. This enabled relatively complex instruction sets in modest CPU (consider that a Motorola 68000, with its many operand modes and eight 32-bit registers, fits in 40000 transistors, whereas a single-core modern x86 will have more than a hundred millions). … Read more
Try using EMON profiling in Vtune, or some equivalent tool like oprof Vtune for Linux (you can search for the Windows version) oprofile EMON (Event Monitoring) profiling => like a time based tool, but it can tell you what performance event is causing the problem. Although, you should start out with a time based profile … Read more
It stands for “End Branch 64 bit” — or more precisely, Terminate Indirect Branch in 64 bit. Here is the operation: IF EndbranchEnabled(CPL) & EFER.LMA = 1 & CS.L = 1 IF CPL = 3 THEN IA32_U_CET.TRACKER = IDLE IA32_U_CET.SUPPRESS = 0 ELSE IA32_S_CET.TRACKER = IDLE IA32_S_CET.SUPPRESS = 0 FI FI; The instruction is otherwise … Read more