Re: [PATCH] mm: use only per-device readahead limit

[Linus Torvalds]

On Fri, Aug 21, 2015 at 10:12 AM, Roman Gushchin <klamm@xxxxxxxxxxxxxx> wrote:
>
> There are devices, which require custom readahead limit.
> For instance, for RAIDs it's calculated as number of devices
> multiplied by chunk size times 2.

So afaik, the default read-ahead size is 128kB, which is actually
smaller than the old 512-page limit.

Which means that you probably changed "ra_pages" somehow. Is it some
system tool that does that automatically, and if so based on what,
exactly?

I'm also slightly worried about the fact that now the max read-ahead
may actually be zero, and/or basically infinite (there's a ioctl to
set it that only tests that it's not negative). Does everything react
ok to that?

               Linus
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