linux-kernel - Re: [PATCH] mm: split thp synchronously on MADV

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Message-ID: <YZnMnyKRk8d/Ilyo@casper.infradead.org>
Date:   Sun, 21 Nov 2021 04:35:43 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Shakeel Butt <shakeelb@...gle.com>
Cc:     David Hildenbrand <david@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: split thp synchronously on MADV_DONTNEED

On Sat, Nov 20, 2021 at 12:12:30PM -0800, Shakeel Butt wrote:
> This patch let such applications not worry about the low level handling
> of THPs in the kernel and splits the THPs synchronously on
> MADV_DONTNEED.

I don't mind the synchronous split, but I have concerns about the
implementation.  I don't think it's worth another pointer in task_struct.
It's also the case that splitting is likely to succeed, so I think a
better implementation would try to split and then put the page on the
global deferred list if splitting fails.