Re: [RFC PATCH] mm: Add large folio support for async readahead

[Yafang Shao <laoar.shao@gmail.com>]

On Tue, Nov 5, 2024 at 12:21 PM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Tue, Nov 05, 2024 at 11:01:01AM +0800, Yafang Shao wrote:
> > Upon further analysis, it appears that the behavior depends on the
> > /sys/block/*/queue/read_ahead_kb setting. On my test server, this
> > parameter is set to 128KB. For the current approach to work without
> > modification, it would need to be 2MB-aligned.
> >
> > However, I believe MADV_HUGEPAGE behavior should not be dependent on
> > the value of read_ahead_kb. It would be more robust if the kernel
> > automatically aligned it to 2MB when MADV_HUGEPAGE is enabled. The
> > following changes ensure compatibility with non-2MB-aligned
> > read_ahead_kb values:
>
> or maybe:
>
> static unsigned long get_next_ra_size(struct file_ra_state *ra,
>                                       unsigned long max)
> {
>         unsigned long cur = ra->size;
>
>         if (cur < max / 16)
>                 return 4 * cur;
>         if (cur <= max / 2)
>                 return 2 * cur;
> +       if (cur > max)
> +               return cur;
>         return max;
> }
>

It is better. Thanks for your suggestion.

-- 
Regards
Yafang