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SubjectRe: clustering page-ins
Chuck Lever wrote:
> true. but i'm also worried about sharing the read-ahead information
> amongst all mappers of a shared file. this case has come up in my
> benchmarking (although i haven't tracked it down, it is occurring in some
> basic commands that are run by the benchmark).

Since each mapping has its own vm_area, I don't see the problem.
Do you want different mappers to share read-ahead info?

> so, i think the information needs to be in the file struct so that shared
> maps don't continue to read ahead a file that is already in the page
> cache.

Sorry I don't quite understand what you want here. If you want to share
read-ahead info between different mappers, struct file isn't going to do
it -- each new open() creates a new struct file. If you don't, vm_area
and struct file won't make much difference.

It's only when you consider multiple mappings made from the same file
descriptor (or passed through fork/exec) that there's a difference: then
struct file leads to sharing while vm_area does not. There's also the
matter of files mapped and read with read() (e.g. ELF executables).

-- Jamie

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