linux-kernel - Re: [PATCH v3 0/7] prctl: introduce PR_SET/GET_THP

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Message-ID: <p3lc5tuzpblwtikfodj5d5wjbpklqwg6oexn4xw3cdwspqwkmy@l7vhj72rjgsb>
Date: Tue, 20 May 2025 22:33:27 -0400
From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
To: Usama Arif <usamaarif642@...il.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, david@...hat.com,
        linux-mm@...ck.org, hannes@...xchg.org, shakeel.butt@...ux.dev,
        riel@...riel.com, ziy@...dia.com, laoar.shao@...il.com,
        baolin.wang@...ux.alibaba.com, lorenzo.stoakes@...cle.com,
        npache@...hat.com, ryan.roberts@....com, vbabka@...e.cz,
        jannh@...gle.com, Arnd Bergmann <arnd@...db.de>,
        linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        kernel-team@...a.com
Subject: Re: [PATCH v3 0/7] prctl: introduce PR_SET/GET_THP_POLICY

* Usama Arif <usamaarif642@...il.com> [250519 18:34]:
> This series allows to change the THP policy of a process, according to the
> value set in arg2, all of which will be inherited during fork+exec:
> - PR_DEFAULT_MADV_HUGEPAGE: This will set VM_HUGEPAGE and clear VM_NOHUGEPAGE
>   for the default VMA flags. It will also iterate through every VMA in the
>   process and call hugepage_madvise on it, with MADV_HUGEPAGE policy.
>   This effectively allows setting MADV_HUGEPAGE on the entire process.
>   In an environment where different types of workloads are run on the
>   same machine, this will allow workloads that benefit from always having
>   hugepages to do so, without regressing those that don't.
> - PR_DEFAULT_MADV_NOHUGEPAGE: This will set VM_NOHUGEPAGE and clear VM_HUGEPAGE
>   for the default VMA flags. It will also iterate through every VMA in the
>   process and call hugepage_madvise on it, with MADV_NOHUGEPAGE policy.
>   This effectively allows setting MADV_NOHUGEPAGE on the entire process.
>   In an environment where different types of workloads are run on the
>   same machine,this will allow workloads that benefit from having
>   hugepages on an madvise basis only to do so, without regressing those
>   that benefit from having hugepages always.
> - PR_THP_POLICY_SYSTEM: This will reset (clear) both VM_HUGEPAGE and
>   VM_NOHUGEPAGE process for the default flags.
> 

Subject seems outdated now?  PR_DEFAULT_ vs PR_SET/GET_THP ?

On that note, doesn't it make sense to change the default mm flag under
PR_SET_MM?  PR_SET_MM_FLAG maybe?

Thanks,
Liam