Re: [PATCH V12] mm/debug: Add tests validating architecture page table helpers
From: Qian Cai <hidden>
Date: 2020-02-03 15:48:22
Also in:
linux-arm-kernel, linux-mips, linux-mm, linux-s390, linux-sh, lkml, sparclinux
On Mon, 2020-02-03 at 16:14 +0100, Christophe Leroy wrote:
Le 02/02/2020 à 12:26, Qian Cai a écrit :quoted
quoted
On Jan 30, 2020, at 9:13 AM, Christophe Leroy [off-list ref] wrote: config DEBUG_VM_PGTABLE bool "Debug arch page table for semantics compliance" if ARCH_HAS_DEBUG_VM_PGTABLE || EXPERT depends on MMU default 'n' if !ARCH_HAS_DEBUG_VM_PGTABLE default 'y' if DEBUG_VMDoes it really necessary to potentially force all bots to run this? Syzbot, kernel test robot etc? Does it ever pay off for all their machine times there?Machine time ? On a 32 bits powerpc running at 132 MHz, the tests takes less than 10ms. Is it worth taking the risk of not detecting faults by not selecting it by default ?
The risk is quite low as Catalin mentioned this thing is not to detect regressions but rather for arch/mm maintainers. I do appreciate the efforts to get everyone as possible to run this thing, so it get more notices once it is broken. However, DEBUG_VM seems like such a generic Kconfig those days that have even been enabled by default for Fedora Linux, so I would rather see a more sensitive default been taken even though the test runtime is fairly quickly on a small machine for now.
[ 5.656916] debug_vm_pgtable: debug_vm_pgtable: Validating architecture page table helpers [ 5.665661] debug_vm_pgtable: debug_vm_pgtable: Validated architecture page table helpers