Re: [PATCH] 2.6 workaround for Athlon/Opteron prefetch errata

Alan Cox
2003-09-15T13:51:02Z

On Llu, 2003-09-15 at 13:11, Bill Davidsen wrote:
> The code to disable prefetch on Athlon is 300 bytes and hurts your PIV?
> Really? I'll dig back through the code, but I recall it as adding or
> deleting an entry in a table to enable prefetch. If it's affecting PIV the
> code to use prefetch is seriously broken.

Big time. Its over 300 bytes long because its embedded in each inline
prefetch and it causes a branch misprediction almost every time. Amazing
what you find when you actually measure stuff 8)

So right now, its faster on PIV to delete the prefetch than use the
current hack, and adding the Athlon fix makes Athlon and PIV faster and
total memory size lower.