linux-kernel - Re: [PATCH v4 5/6] mm,thp: add read-only THP support for (non-shmem) FS

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Date:   Thu, 20 Jun 2019 17:33:25 +0000
From:   Rik van Riel <riel@...com>
To:     Song Liu <songliubraving@...com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
CC:     "matthew.wilcox@...cle.com" <matthew.wilcox@...cle.com>,
        "kirill.shutemov@...ux.intel.com" <kirill.shutemov@...ux.intel.com>,
        "Kernel Team" <Kernel-team@...com>,
        "william.kucharski@...cle.com" <william.kucharski@...cle.com>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4 5/6] mm,thp: add read-only THP support for (non-shmem)
 FS

On Thu, 2019-06-20 at 10:27 -0700, Song Liu wrote:
> This patch is (hopefully) the first step to enable THP for non-shmem
> filesystems.
> 
> This patch enables an application to put part of its text sections to
> THP
> via madvise, for example:
> 
>     madvise((void *)0x600000, 0x200000, MADV_HUGEPAGE);
> 
> We tried to reuse the logic for THP on tmpfs.
> 
> Currently, write is not supported for non-shmem THP. khugepaged will
> only
> process vma with VM_DENYWRITE. The next patch will handle writes,
> which
> would only happen when the vma with VM_DENYWRITE is unmapped.
> 
> An EXPERIMENTAL config, READ_ONLY_THP_FOR_FS, is added to gate this
> feature.
> 
> Signed-off-by: Song Liu <songliubraving@...com>

Acked-by: Rik van Riel <riel@...riel.com>

(I suppose I should have sent this out last night,
while I was posting questions about patch 6)