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@travisdowns
travisdowns / cache-counters-rant.md
Created October 13, 2019 16:46
Discussion of x86 L1D related cache counters

The counters that are the easiest to understand and the best for making ratios that are internally consistent (i.e., always fall in the range 0.0 to 1.0) are the mem_load_retired events, e.g., mem_load_retired.l1_hit and mem_load_retired.l1_miss.

These count at the instruction level, i.e., the universe of retired instructions. For example, could make a reasonable hit ratio from mem_load_retired.l1_hit / mem_inst_retired.all_loads and it will be sane (never indicate a hit rate more than 100%, for example).

That one isn't perfect though, in that it may not reflect the true costs of cache misses and the behavior of the program for at least the following reasons:

  • It appplies only to loads and can't catch misses imposed by stores (AFAICT there is no event that counts store misses).
  • It only counts loads that retire - a lot of the load activity in your process may be due to loads on a speculative path that never retire. Loads on a speculative path may bring in data that is never used, causing misses and d
@zeux
zeux / luau_features.pdf
Last active May 22, 2024 23:40
Frequently asked questions about the Lua VM work we (Roblox) are doing.
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@pkhuong
pkhuong / u4.c
Created December 24, 2017 05:04
#include <assert.h>
#include <err.h>
#include <inttypes.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <emmintrin.h>
#include <tmmintrin.h>
@bkaradzic
bkaradzic / orthodoxc++.md
Last active November 17, 2024 00:54
Orthodox C++

Orthodox C++

What is Orthodox C++?

Orthodox C++ (sometimes referred as C+) is minimal subset of C++ that improves C, but avoids all unnecessary things from so called Modern C++. It's exactly opposite of what Modern C++ suppose to be.

Why not Modern C++?

@mpasternacki
mpasternacki / freebsd_on_mbp.md
Created January 23, 2015 17:12
FreeBSD on a MacBook Pro

FreeBSD on a MacBook Pro

Since 2008 or 2009 I work on Apple hardware and OS: back then I grew tired of Linux desktop (which is going to be MASSIVE NEXT YEAR, at least since 2001), and switched to something that Just Works. Six years later, it less and less Just Works, started turning into spyware and nagware, and doesn't need much less maintenance than Linux desktop — at least for my work, which is system administration and software development, probably it is better for the mythical End User person. Work needed to get software I need running is not less obscure than work I'd need to do on Linux or othe Unix-like system. I am finding myself turning away from GUI programs that I used to appreciate, and most of the time I use OSX to just run a terminal, Firefox, and Emacs. GUI that used to be nice and unintrusive, got annoying. Either I came full circle in the last 15 years of my computer usage, or the OSX experience degraded in last 5 years. Again, this is from a sysadmin/developer ki

@panzi
panzi / portable_endian.h
Last active August 9, 2024 13:12
This provides the endian conversion functions form endian.h on Windows, Linux, *BSD, Mac OS X, and QNX. You still need to use -std=gnu99 instead of -std=c99 for gcc. The functions might actually be macros. Functions: htobe16, htole16, be16toh, le16toh, htobe32, htole32, be32toh, le32toh, htobe64, htole64, be64toh, le64toh. License: I hereby put …
// "License": Public Domain
// I, Mathias Panzenböck, place this file hereby into the public domain. Use it at your own risk for whatever you like.
// In case there are jurisdictions that don't support putting things in the public domain you can also consider it to
// be "dual licensed" under the BSD, MIT and Apache licenses, if you want to. This code is trivial anyway. Consider it
// an example on how to get the endian conversion functions on different platforms.
#ifndef PORTABLE_ENDIAN_H__
#define PORTABLE_ENDIAN_H__
#if (defined(_WIN16) || defined(_WIN32) || defined(_WIN64)) && !defined(__WINDOWS__)