On Wed, 26 Jul 2023 10:59:32 +0530 Aneesh Kumar K V <aneesh.kumar@xxxxxxxxxxxxx> wrote: > On 7/26/23 12:59 AM, Andrew Morton wrote: > > On Tue, 25 Jul 2023 00:37:46 +0530 "Aneesh Kumar K.V" <aneesh.kumar@xxxxxxxxxxxxx> wrote: > > > >> This patch series implements changes required to support DAX vmemmap > >> optimization for ppc64. > > > > Do we have any measurements to help us understand the magnitude > > of this optimization? > > > > And any documentation which helps users understand whether and > > why they should enable this feature? > > That is memory space optimization due to kernel reusing the tail page struct pages. The details > of the optimization is documented in patch 11. We document there the impact with both 4k and > 64K page size. I suppose that with sufficient arithmetic one could use Documentation/powerpc/vmemmap_dedup.rst to figure out the bottom-line savings. I was more expecting a straightforward statement in the [0/N] overview to help people understand why they're reading this patchset at all. Like "saves 5% of total memory on my XXX machine".
