Re: [PATCH 0/7] enable PT_RECLAIM on all 64-bit architectures

Qi Zheng
2025-11-18T11:55:17Z

On 11/18/25 12:53 AM, David Hildenbrand (Red Hat) wrote:
> On 14.11.25 12:11, Qi Zheng wrote:
>> From: Qi Zheng <zhengqi.arch@bytedance.com>
>>
>> Hi all,
>>
>> This series aims to enable PT_RECLAIM on all 64-bit architectures.
>>
>> On a 64-bit system, madvise(MADV_DONTNEED) may cause a large number of
>> empty PTE
>> page table pages (such as 100GB+). To resolve this problem, we need to
>> enable
>> PT_RECLAIM, which depends on MMU_GATHER_RCU_TABLE_FREE.
>>
>
> Makes sense!
>
>> Therefore, this series first enables MMU_GATHER_RCU_TABLE_FREE on all
>> 64-bit
>> architectures, and finally makes PT_RECLAIM depend on
>> MMU_GATHER_RCU_TABLE_FREE
>> && 64BIT. This way, PT_RECLAIM can be enabled by default on all 64-bit
>> architectures.
>
> Could we then even go ahead and stop making PT_RECLAIM user-selectable?

OK, will change to:

config PT_RECLAIM
def_bool y
depends on MMU_GATHER_RCU_TABLE_FREE && MMU && SMP && 64BIT

>