| Message ID | 1541421211-17561-1-git-send-email-zhangkehong@hisilicon.com (mailing list archive) |
|---|---|
| State | RFC |
| Headers | show |
| Series | [RFC] arm64: Kconfig: Choose ARM64_64K_PAGES as default | expand |
Hi, On 05/11/18 12:33, Kehong Zhang wrote: > For arm64 performance considerations, change default page size to 64K. defconfig never stands for performance. If that was the case, we must remove other options that could potentially slow down the performance. defconfig could be interpreted as more of a "standard" config which gives the best effort to make sure you get a usable system overall. With this change, a rootfs with AArch32 applications without 64K aligned segments would fail, and that breaks the assumption about defconfig. So, NAK from my side. Btw, please could you share any performance numbers from the comparison with 4K kernel ? Suzuki > > Cc: Catalin Marinas <catalin.marinas@arm.com>; > Cc: Will Deacon <will.deacon@arm.com>; > Signed-off-by: Kehong Zhang <zhangkehong@hisilicon.com> > --- > arch/arm64/Kconfig | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig > index 787d785..56f651f 100644 > --- a/arch/arm64/Kconfig > +++ b/arch/arm64/Kconfig > @@ -620,7 +620,7 @@ endmenu > > choice > prompt "Page size" > - default ARM64_4K_PAGES > + default ARM64_64K_PAGES > help > Page size (translation granule) configuration. > > @@ -639,10 +639,10 @@ config ARM64_16K_PAGES > config ARM64_64K_PAGES > bool "64KB" > help > - This feature enables 64KB pages support (4KB by default) > - allowing only two levels of page tables and faster TLB > - look-up. AArch32 emulation requires applications compiled > - with 64K aligned segments. > + This feature enables 64KB pages support allowing only two > + levels of page tables and faster TLB look-up. AArch32 > + emulation requires applications compiled with 64K aligned > + segments. > > endchoice > >
On 05/11/2018 14:08, Suzuki K Poulose wrote: > Hi, > > On 05/11/18 12:33, Kehong Zhang wrote: >> For arm64 performance considerations, change default page size to 64K. > > defconfig never stands for performance. If that was the case, we must > remove other options that could potentially slow down the performance. > > defconfig could be interpreted as more of a "standard" config which > gives the best effort to make sure you get a usable system overall. > With this change, a rootfs with AArch32 applications without 64K aligned > segments would fail, and that breaks the assumption about defconfig. Plus I think it's still the case that various drivers and filesystems just don't work properly with PAGE_SIZE != 4K, and reducing defconfig's development/testing coverage is exactly what we don't want. If you're building a distro or running production workloads with an unmodified defconfig, you're probably doing it wrong. Robin. > So, NAK from my side. > > Btw, please could you share any performance numbers from the comparison > with 4K kernel ? > > Suzuki > >> >> Cc: Catalin Marinas <catalin.marinas@arm.com>; >> Cc: Will Deacon <will.deacon@arm.com>; >> Signed-off-by: Kehong Zhang <zhangkehong@hisilicon.com> >> --- >> arch/arm64/Kconfig | 10 +++++----- >> 1 file changed, 5 insertions(+), 5 deletions(-) >> >> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig >> index 787d785..56f651f 100644 >> --- a/arch/arm64/Kconfig >> +++ b/arch/arm64/Kconfig >> @@ -620,7 +620,7 @@ endmenu >> choice >> prompt "Page size" >> - default ARM64_4K_PAGES >> + default ARM64_64K_PAGES >> help >> Page size (translation granule) configuration. >> @@ -639,10 +639,10 @@ config ARM64_16K_PAGES >> config ARM64_64K_PAGES >> bool "64KB" >> help >> - This feature enables 64KB pages support (4KB by default) >> - allowing only two levels of page tables and faster TLB >> - look-up. AArch32 emulation requires applications compiled >> - with 64K aligned segments. >> + This feature enables 64KB pages support allowing only two >> + levels of page tables and faster TLB look-up. AArch32 >> + emulation requires applications compiled with 64K aligned >> + segments. >> endchoice >> > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 787d785..56f651f 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -620,7 +620,7 @@ endmenu choice prompt "Page size" - default ARM64_4K_PAGES + default ARM64_64K_PAGES help Page size (translation granule) configuration. @@ -639,10 +639,10 @@ config ARM64_16K_PAGES config ARM64_64K_PAGES bool "64KB" help - This feature enables 64KB pages support (4KB by default) - allowing only two levels of page tables and faster TLB - look-up. AArch32 emulation requires applications compiled - with 64K aligned segments. + This feature enables 64KB pages support allowing only two + levels of page tables and faster TLB look-up. AArch32 + emulation requires applications compiled with 64K aligned + segments. endchoice
For arm64 performance considerations, change default page size to 64K. Cc: Catalin Marinas <catalin.marinas@arm.com>; Cc: Will Deacon <will.deacon@arm.com>; Signed-off-by: Kehong Zhang <zhangkehong@hisilicon.com> --- arch/arm64/Kconfig | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)