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Subject: Re: [PATCH V12] mm/debug: Add tests validating architecture page
 table helpers
To:     Qian Cai <cai@lca.pw>
Cc:     Anshuman Khandual <Anshuman.Khandual@arm.com>, linux-mm@kvack.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>,
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From:   Christophe Leroy <christophe.leroy@c-s.fr>
Message-ID: <8e94a073-4045-89aa-6a3b-24847ad7c858@c-s.fr>
Date:   Mon, 3 Feb 2020 16:14:24 +0100
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Le 02/02/2020 à 12:26, Qian Cai a écrit :
> 
> 
>> On Jan 30, 2020, at 9:13 AM, Christophe Leroy <christophe.leroy@c-s.fr> 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_VM
> 
> Does 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 ?

[    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

Christophe