linux-kernel - Re: [RFC PATCH 0/3] asynchronously scan and free empty user PTE pages

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Message-ID: <fbd652ad-2f3f-4fa7-9a4c-96e0876b6397@redhat.com>
Date: Mon, 17 Jun 2024 19:51:31 +0200
From: David Hildenbrand <david@...hat.com>
To: Qi Zheng <zhengqi.arch@...edance.com>
Cc: hughd@...gle.com, willy@...radead.org, mgorman@...e.de,
 muchun.song@...ux.dev, akpm@...ux-foundation.org, linux-mm@...ck.org,
 linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] asynchronously scan and free empty user PTE pages

On 14.06.24 05:32, Qi Zheng wrote:
> Hi David,
> 
> How about starting with this:
> 
> a. for MADV_DONTNEED case, try synchronous reclaim as you said
> b. for MADV_FREE case, add a madvise(MADV_PT_RECLAIM) option to mark
>      this vma, then add its corresponding mm to a global list, and then
>      traverse the list and reclaim it when the memory is tight and enters
>      the system reclaim path.
> 
>      (If this option is for synchronous reclaim as you said, then the
>       user-mode program may need to start a thread to make a cyclic call.
>       I'm not sure if this usage makes sense. If so, I can also implement
>       such an option.)
> c. for s390 case you mentioned, maybe we can set a CONFIG_FREE_PT first,
>      and then s390 will not select this config until the problem is solved.

CONFIG_PT_RECLAIM or sth. like that, that would depend on 
CONFIG_ARCH_SUPPORTS_PT_RECLAIM.

Then we can start with what we know works and was tested (e.g., x86).

-- 
Cheers,

David / dhildenb