Re: hashed waitqueues

Andrew Morton
2002-01-04T23:12:34Z

William Lee Irwin III wrote:
>
> This is a long-discussed space optimization for the VM system, with
> what is expected to be a minor time tradeoff.

Nice code.

> ...
> + /*
> + * Although the default semantics of wake_up() are
> + * to wake all, here the specific function is used
> + * to make it even more explicit that a number of
> + * pages are being waited on here.
> + */
> + if(waitqueue_active(page_waitqueue(page)))
> + wake_up_all(page_waitqueue(page));

Does the compiler CSE these two calls to page_waitqueue()?
All versions? I'd be inclined to do CSE-by-hand here.

Also, why wake_up_all()? That will wake all tasks which are sleeping
in __lock_page(), even though they've asked for exclusive wakeup
semantics. Will a bare wake_up() here not suffice?

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