linux-kernel - Re: [v3 PATCH 0/8] Make khugepaged collapse readonly FS THP more consistent

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Message-ID: <YkuKbMbSecBVsa1k@casper.infradead.org>
Date:   Tue, 5 Apr 2022 01:16:44 +0100
From:   Matthew Wilcox <willy@...radead.org>
To:     Yang Shi <shy828301@...il.com>
Cc:     vbabka@...e.cz, kirill.shutemov@...ux.intel.com,
        linmiaohe@...wei.com, songliubraving@...com, riel@...riel.com,
        ziy@...dia.com, tytso@....edu, akpm@...ux-foundation.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [v3 PATCH 0/8] Make khugepaged collapse readonly FS THP more
 consistent

On Mon, Apr 04, 2022 at 01:02:42PM -0700, Yang Shi wrote:
> The readonly FS THP relies on khugepaged to collapse THP for suitable
> vmas.  But it is kind of "random luck" for khugepaged to see the
> readonly FS vmas (see report: https://lore.kernel.org/linux-mm/00f195d4-d039-3cf2-d3a1-a2c88de397a0@suse.cz/) since currently the vmas are registered to khugepaged when:

I still don't see the point.  The effort should be put into
supporting large folios, not in making this hack work better.