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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).

Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.

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I FIXED AMD's Preferred Core Linux patch to FINALLY work for HIGHER BOOST and PERFORMANCE ! (www.youtube.com)

submitted 1 year ago by [email protected] to c/[email protected]

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[–] [email protected] 5 points 1 year ago (3 children)

Apparently there's a bug in an AMD's driver. It was supposed to assign processes based on each core's self reported performance, but because of the bug it was random.

This "self reported performance" is based on evaluation done to the cores in the fab process, by AMD. Meaning, due to imperfections some cores are a bit better than others.

[–] NoXPhasma 9 points 1 year ago* (last edited 1 year ago) (2 children)

It's not just random, it simply does not even work. Because they set this:

+/*Preferred Core featue is supported*/
+static bool prefcore = true;

And later in the code they do the if condition wrong:

+	if (prefcore)
+		WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);
+	else
+		WRITE_ONCE(cpudata->highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));

if should look like this:

+	if (prefcore)
+		WRITE_ONCE(cpudata->highest_perf, AMD_CPPC_HIGHEST_PERF(cap1));
+	else
+		WRITE_ONCE(cpudata->highest_perf, AMD_PSTATE_PREFCORE_THRESHOLD);

There is probably even more wrong, looking at the code quality, but this at least makes the preferred core work.

[–] [email protected] 2 points 1 year ago* (last edited 1 year ago) (1 children)

I don't know if we're discussing semantics. A performance score is attributed, and before the fix their scores were all 166. It doesn't work, as you said. So the consequence is the preferred core being "random", isn't it?

[–] NoXPhasma 1 points 1 year ago

I don't know if it's random, the CPU scheduler still decides what thread to use. It will have its own semantics, but I don't know on what those are based.