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

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Message-ID: <f7f0ca8d-bca2-4a3e-8c45-85cba1b0ff18@gmail.com>
Date: Tue, 18 Nov 2025 19:53:50 +0800
From: Qi Zheng <arch0.zheng@...il.com>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>,
 Qi Zheng <qi.zheng@...ux.dev>, 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 11/18/25 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:

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

>