On 02.07.22 06:24, Andrew Morton wrote: > On Wed, 29 Jun 2022 16:53:51 -0600 Khalid Aziz <khalid.aziz@xxxxxxxxxx> wrote: > >> This patch series implements a mechanism in kernel to allow >> userspace processes to opt into sharing PTEs. It adds a new >> in-memory filesystem - msharefs. > > Dumb question: why do we need a new filesystem for this? Is it not > feasible to permit PTE sharing for mmaps of tmpfs/xfs/ext4/etc files? > IIRC, the general opinion at LSF/MM was that this approach at hand is makes people nervous and I at least am not convinced that we really want to have this upstream. What's *completely* missing from the cover letter are the dirty details: "Actual data is mmap'ed using anonymous pages, ext4/xfs/btfrfs/etc files.". Gah. As raised already, "anonymous pages" makes me shiver. (To me, what I read, this looks like an RFC to me, yet I see "v2". But I am a little confused why most of the feedback at LSF/MM seems to be ignored and people are moving forward with this approach. But maybe my memory is wrong.) Please, let's look into more generic page table sharing just like hugetlb already provides to some degree. And if we need additional alignment requirements to share multiple page table levels, then let's look into that as well for special users. -- Thanks, David / dhildenb
