Re: [PATCH v3 0/5] ksm: support tracking KSM-placed zero-pages

[David Hildenbrand]

On 19.10.22 00:54, Andrew Morton wrote:
> On Tue, 18 Oct 2022 09:00:22 +0000 xu xin <xu.xin.sc@xxxxxxxxx> wrote:
>
> > > A full description of the real-world end-user operational benefits of
> > > these changes would help, please.
> >
> > The core idea of this patch set is to enable users to perceive the number of any
> > pages merged by KSM, regardless of whether use_zero_page switch has been turned
> > on, so that users can know how much free memory increase is really due to their
> > madvise(MERGEABLE) actions.
>
> OK, thanks.
>
> > The motivation for me to do this is that when I do
> > an application optimization of KSM on embedded Linux for 5G platform, I find
> > that ksm_merging_pages of some process becomes very small(but used to be large),
> > which led me to think that there was any problem with the application KSM-madvise
> > strategy, but in fact, it was only because use_zero_pages is on.
>
> Please expand on the above motivation and experience, and include it in
> the [0/n] changelog.  But let's leave it a few days to see if there's
> additional reviewer input.

I just posted a selftest:

https://lore.kernel.org/all/20221021101141.84170-5-david@xxxxxxxxxx/T/#u

That could (should) be extended to test if unmerging works as expected.


Having that said, I think we really want a second pair of (KSM-expert) 
eyes on these changes before moving forward with them.

--
Thanks,

David / dhildenb