Re: [PATCH v3 2/2] ksm: Optimize rmap_walk_ksm by passing a suitable address range

[Andrew Morton]

On Tue, 7 Apr 2026 10:43:12 +0100 "Lorenzo Stoakes (Oracle)" <ljs@xxxxxxxxxx> wrote:

> > Thanks, Hugh.   Administreevia:
> >
> > I've removed this patch from the mm-stable branch and I reworked its
> > [1/2] "ksm: initialize the addr only once in rmap_walk_ksm" to be
> > presented as a singleton patch.
> >
> > For now I've restaged this patch ("ksm: optimize rmap_walk_ksm by
> > passing a suitable address range") at the tail of the mm-unstable
> > branch and I'll enter wait-and-see mode.
> >
> 
> Given we're at -rc7 now, I think we should delay this patch until 7.2, unless
> I'm much mistaken wrt Hugh's concerns.
> 
> I'm concerned this is a subtle way of breaking things so we really want to be
> confident.
> 
> We should also bundle up the test at
> https://lore.kernel.org/all/20260407140805858ViqJKFhfmYSfq0FynsaEY@xxxxxxxxxx/
> with this patch (should we find it's ok) as a separate series.
> 
> Really overall I think safest to yank until 7.2 honestly.

OK.  But let's not lose sight of those potential efficiency gains:

         Time_ms      Nr_iteration_total    Skip_addr_out_of_range   Skip_mm_mismatch
Before:  228.65       22169                 22168                    0
After :   0.396        3                     0                       2