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Date:   Wed, 3 Jun 2020 14:51:22 -0700
From:   Matthew Wilcox <willy@infradead.org>
To:     Hugh Dickins <hughd@google.com>
Cc:     Johannes Weiner <hannes@cmpxchg.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Song Liu <songliubraving@fb.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] mm,thp: stop leaking unreleased file pages
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References: <alpine.LSU.2.11.2005231837500.1766@eggly.anvils>
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On Wed, May 27, 2020 at 02:28:10PM -0700, Hugh Dickins wrote:
> Saying "source inspection" reminds me: there is another funny in there,
> but I don't think it matters very much in practice, and might need
> rather a lot of testing to justify any particular patch: where
> page_cache_sync_readahead() asks for PAGE_SIZE pages!
> 
> "end - index" seems a more reasonable number to me: but then we
> might find that reading ahead into the next huge extent had actually
> been a useful optimization (and those readahead functions impose
> their own caps, so PAGE_SIZE shouldn't work out too outrageously).

That readahead was only added in 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0
so it probably hasn't really been performance tested yet.