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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <afecde77-a4af-40f1-a905-9de8a1bdd783@kernel.org>
Date: Wed, 19 Nov 2025 11:13:37 +0100
From: "David Hildenbrand (Red Hat)" <david@...nel.org>
To: Qi Zheng <arch0.zheng@...il.com>, 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 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?

-- 
Cheers

David