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

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Message-ID: <83e88171-54cb-4112-a344-f6a7d7f13784@kernel.org>
Date: Mon, 17 Nov 2025 17:53:42 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: 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 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?

-- 
Cheers

David