Re: [PATCH] riscv: enable THP_SWAP for RV64

[Conor Dooley <conor.dooley@microchip.com>]

On Wed, Oct 05, 2022 at 07:35:53PM -0700, Palmer Dabbelt wrote:
> On Sun, 21 Aug 2022 10:05:59 PDT (-0700), jszhang@kernel.org wrote:
> > I have a Sipeed Lichee RV dock board which only has 512MB DDR, so
> > memory optimizations such as swap on zram are helpful. As is seen
> > in commit d0637c505f8a ("arm64: enable THP_SWAP for arm64") and
> > commit bd4c82c22c367e ("mm, THP, swap: delay splitting THP after
> > swapped out"), THP_SWAP can improve the swap throughput significantly.
> > 
> > Enable THP_SWAP for RV64, testing the micro-benchmark which is
> > introduced by commit d0637c505f8a ("arm64: enable THP_SWAP for arm64")
> > shows below numbers on the Lichee RV dock board:
> > 
> > thp swp throughput w/o patch: 66908 bytes/ms (mean of 10 tests)
> > thp swp throughput w/ patch: 322638 bytes/ms (mean of 10 tests)
> > 
> > Improved by 382%!
> > 
> > Signed-off-by: Jisheng Zhang <jszhang@kernel.org>
> > ---
> >  arch/riscv/Kconfig | 1 +
> >  1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> > index ed66c31e4655..19088c750c7f 100644
> > --- a/arch/riscv/Kconfig
> > +++ b/arch/riscv/Kconfig
> > @@ -45,6 +45,7 @@ config RISCV
> >  	select ARCH_WANT_FRAME_POINTERS
> >  	select ARCH_WANT_GENERAL_HUGETLB
> >  	select ARCH_WANT_HUGE_PMD_SHARE if 64BIT
> > +	select ARCH_WANTS_THP_SWAP if TRANSPARENT_HUGEPAGE
> >  	select BINFMT_FLAT_NO_DATA_START_OFFSET if !MMU
> >  	select BUILDTIME_TABLE_SORT if MMU
> >  	select CLONE_BACKWARDS
> 
> Thanks, this is on for-next.

FYI, this is v1 of a patchset that went to v3.
v3 only changed the commit message, but v2 had a functional change.

v3 is here:
https://lore.kernel.org/all/20220829145742.3139-1-jszhang@kernel.org/

Thanks,
Conor.