Re: [linus:master] [x86] 4817f70c25: stress-ng.mmapaddr.ops_per_sec 63.0% regression

[David Hildenbrand]

On 28.01.25 14:28, Peter Zijlstra wrote:
> On Tue, Jan 28, 2025 at 12:39:51PM +0100, David Hildenbrand wrote:
> > On 28.01.25 12:31, Peter Zijlstra wrote:
>
> > > > I recall a recent series to select MMU_GATHER_RCU_TABLE_FREE on x86
> > > > unconditionally (@Peter, @Rik).
> > >
> > > Those changes should not have made it to Linus yet.
> > >
> > > /me updates git and checks...
> > >
> > > nope, nothing changed there ... yet
> >
> > Sorry, I wasn't quite clear. CONFIG_PT_RECLAIM made it upstream, which has
> > "select MMU_GATHER_RCU_TABLE_FREE" in kconfig.
> >
> > So I'm wondering if the degradation we see in this report is due to
> > MMU_GATHER_RCU_TABLE_FREE being selected by CONFIG_PT_RECLAIM, and we'd get
> > the same result (degradation) when unconditionally enabling
> > MMU_GATHER_RCU_TABLE_FREE.
>
> Ah, yes, put a RHEL based config (as is the case here) should already
> have it selected due to PARAVIRT.

Ah, right. Most distros will just have it enabled either way.

But that would then mean that MMU_GATHER_RCU_TABLE_FREE is not the cause 
for the regression here, and something else is going wrong.

--
Cheers,

David / dhildenb