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

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Message-ID: <9c884aeb-c1ec-4fe0-8495-639344633569@linux.dev>
Date: Wed, 19 Nov 2025 18:37:47 +0800
From: Qi Zheng <qi.zheng@...ux.dev>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>, will@...nel.org,
 aneesh.kumar@...nel.org, npiggin@...il.com, peterz@...radead.org,
 dev.jain@....com, akpm@...ux-foundation.org, ioworker0@...il.com
Cc: linux-arch@...r.kernel.org, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org, linux-alpha@...r.kernel.org,
 linux-snps-arc@...ts.infradead.org, loongarch@...ts.linux.dev,
 linux-mips@...r.kernel.org, linux-parisc@...r.kernel.org,
 linux-um@...ts.infradead.org, Qi Zheng <zhengqi.arch@...edance.com>
Subject: Re: [PATCH 0/7] enable PT_RECLAIM on all 64-bit architectures



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@...edance.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.

>