Re: [PATCH] x86/vdso: Use non-serializing instruction rdtsc

[Dave Hansen]

On 5/15/23 23:52, Rong Tao wrote:
> Replacing rdtscp or 'lfence;rdtsc' with the non-serializable instruction
> rdtsc can achieve a 40% performance improvement with only a small loss of
> precision.

I think the minimum that can be done in a changelog like this is to
figure out _why_ a RDTSCP was in use.  There are a ton of things that
can make the kernel go faster, but not all of them are a good idea.

I assume that the folks that wrote this had good reason for not using
plain RSTSC.  What were those reasons?