Re: [PATCH v2 0/3] x86/fred: enable FRED by default

[Andy Lutomirski]

On Fri, Mar 27, 2026, at 6:20 PM, H. Peter Anvin wrote:
> On 2026-03-26 15:11, Andy Lutomirski wrote:
>> 
>> Those performance increases while with fio / io_uring are ridiculous.  I wonder whether anyone can looked at /proc/interrupts to try to figure out what's going on.  I imagine we're bottlenecking on IO interrupts or something and FRED speeds that up by a factor of several, but this makes me wonder whether there's some tuning that should be done.
>> 
>> Jens, for background, FRED ought to speed up page faults and interrupts (both IPI and device) by a considerable amount -- maybe a reduction of 20k or more cycles per interrupt.  But Phoronix is showing up to a factor of 2 (!) actual performance increase using io_uring with a job count of 8.  Now maybe 8 is too small, but I'm wondering whether the io_uring or IO part is missing some optimization that it ought to have.
>> 
>
> Hi Andy! Long time no C!
>
> Either way, I presume neither of you have any problems with the patchset itself?

I'm fine with the patchset, except that maybe we should deal with the syscall reg issue in the same release.

--Andy

>
> 	-hpa