Re: [PATCH -next 0/2] riscv/mm: Enable THP migration

[Palmer Dabbelt]

On Wed, 29 Dec 2021 22:45:57 PST (-0800), sunnanyong@xxxxxxxxxx wrote:
> Hi Palmer,
>
> This patchset has been sent for one month ago, I was wondering if you could
>
> have a review and give a feedback please, thanks.

Sorry for being slow, the queue got long over the holidays and I'm still 
trying to dig out.  I was kind of worried about losing some bits, but I 
don't think it's actually that big of a deal -- it's not like there's 
really any user ABI here, aside from being able to use less swap.  If 
someone wants to fix that I'm all ears, but I don't think it's worth 
waiting.

This is on for-next.

Thanks!

> On 2021/11/23 22:06, Nanyong Sun wrote:
> > This series enables THP migration on riscv via ARCH_ENABLE_THP_MIGRATION.
> > But first this adjusts PAGE_PROT_NONE to satisfy generic memory semantics
> > like the behavior of pmd_present() and pmd_trans_huge() when in
> > THP splitting or migration.
> >
> > This feature can reduce the time of THP migration by not splits THP
> > before migration and can guarantee the pages after migration are still
> > contiguous.[1]
> >
> > I have tested the below test case on qemu based on riscv after
> > enabling this feature, the throughput of THP migration gains 13x
> > performance improvement:
> > https://github.com/x-y-z/thp-migration-bench
> >
> > I also have tested and passed the test cases under
> > tools/testing/selftests/vm.
> >
> > [1]: https://lwn.net/Articles/723764/
> >
> > Nanyong Sun (2):
> >    riscv/mm: Adjust PAGE_PROT_NONE to comply with THP semantics
> >    riscv/mm: Enable THP migration
> >
> >   arch/riscv/Kconfig                    |  1 +
> >   arch/riscv/include/asm/pgtable-bits.h |  2 +-
> >   arch/riscv/include/asm/pgtable.h      | 16 +++++++++++-----
> >   3 files changed, 13 insertions(+), 6 deletions(-)