Re: DRM lock ordering fix series

[Brice Goglin]

Peter Zijlstra wrote:
> Also note that doing large gup() with gup_fast() will be undesirable due
> to it disabling IRQs. So iterating say several MB worth of pages will
> hurt like crazy. Currently all gup_fast() users do a single page lookup.
>   

In 2.6.29, fs/bio.c:955, fs/direct-io.c:153 and fs/splice.c:1222 do
multiple-pages lookup at once. The latter might be limited to 16 pages
because of the pipe-depth, I don't know about the formers.

Is there some sort of reasonable limit? A couple dozens pages at once maybe?

Brice

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