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x86 asm: move exchange instructions from x86-assembly-cheat

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Ciro Santilli 六四事件 法轮功
2019-06-26 00:00:00 +00:00
parent 88a1c914c9
commit ce3d546ac8
5 changed files with 117 additions and 8 deletions
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userland/cpp/atomic.cpp
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@@ -1,19 +1,27 @@
// https://github.com/cirosantilli/linux-kernel-module-cheat#atomic
// https://github.com/cirosantilli/linux-kernel-module-cheat#cpp
// https://github.com/cirosantilli/linux-kernel-module-cheat#x86-lock-prefix
//
// More restricted than mutex as it can only protect a few operations on integers.
// The non-atomic counters have undefined values which get printed:
// they are extremely likely to be less than the correct value due to
// race conditions on the data read and update of the ++.
//
// But if that is the use case, may be more efficient.
// The atomic counters have defined values, and are asserted
//
// On GCC 4.8 x86-64, using atomic is a huge peformance improvement
// over the same program with mutexes (5x).
// Atomic operations are more restricted than mutex as they can
// only protect a few operations on integers.
//
// But when they can be used, they can be much more efficient than mutees.
//
// On GCC 4.8 x86-64, using atomic offered a 5x peformance improvement
// over the same program with mutexes.
#if __cplusplus >= 201103L
#include <atomic>
#include <cassert>
#include <iostream>
#include <thread>
#include <vector>
#if __cplusplus >= 201103L
std::atomic_ulong my_atomic_ulong(0);
unsigned long my_non_atomic_ulong = 0;
#if defined(__x86_64__)