The Time Stamp Counter was once an excellent high-resolution, low-overhead way for a program to get CPU timing information. With the advent of multi-core/hyper-threaded CPUs, systems with multiple CPUs, and hibernating operating systems, the TSC cannot be relied upon to provide accurate results — unless great care is taken to correct the possible flaws: rate of tick and whether all cores (processors) have identical values in their time-keeping registers. There is no p… WebOn a UP system, CPU TSC sync behavior among multiple cores is determined by CPU TSC capability. Whereas on a SMP system, the TSC sync problem cross multiple CPU sockets could be a big problem. ... The RDTSC instruction is not a serializing instruction. It does not necessarily wait until all previous instructions have been executed before ...
RDTSC the only way to benchmark. - Medium
WebWhen the flag is clear, the RDTSC instruction can be executed at any privilege level; when … WebMar 3, 2024 · x86_64 processor: Brand: AuthenticAMD Model: AMD EPYC 7742 64-Core Processor Invariant TSC: True cpuid leaf 15H is not supported From measurement frequency 2.25 GHz => 444.46 ps Sanity check against std::chrono::steady_clock gives frequency 2.25 GHz => 444.43 ps Measured granularity = 22 ticks => 102.27 MHz, 9.78 ns spanish chinese food near me
[Solved] How to get the CPU cycle count in x86_64 from C++?
WebJul 4, 2010 · Unfortunately the documents don't seem to go into much detail on this, but on Intel machines it seems that the invariant TSC is the same across all cores - I guess either they share the same invariant timer, or the timer rates are the same on all cores (which it should be) and they all get reset at the same time (which they should be). WebJan 5, 2024 · That test uses RDTSC to take samples with better than millisecond precision. Increasing iteration count per sample lets the test cover a longer duration to capture quick clock speed shifts, but without creating a gigantic spreadsheet of doom. I also ran the test on every core. Results were consistent on the same core, but not across cores. WebSep 11, 2014 · When I am running at exactly the nominal 2.7 GHz (core ratio = 27), I see a minimum RDTSC delta of 28. This delta occurred 99 times out of 100 in each of the 5 tests that I ran. At the lowest supported frequency of 1.2 GHz, the minimum RDTSC delta was 63, which also corresponds to 28 core clock cycles. tear scanline