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

Qi Zheng
2025-11-19T10:38:08Z

On 11/19/25 6:13 PM, David Hildenbrand (Red Hat) wrote:
> On 18.11.25 12:53, Qi Zheng wrote:
>>
>>
>> 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:
>
> Was more of a question: is there any scenario where we ran so far into
> issues with it?

No, I haven't received any reports of related issues, either within the
company or in the community.

>