Re: [PATCH RFC 05/15] migration: Simplify unqueue_page()

[Juan Quintela <quintela@redhat.com>]

Peter Xu <peterx@redhat.com> wrote:
> This patch simplifies unqueue_page() on both sides of it (itself, and caller).
>
> Firstly, due to the fact that right after unqueue_page() returned true, we'll
> definitely send a huge page (see ram_save_huge_page() call - it will _never_
> exit before finish sending that huge page), so unqueue_page() does not need to
> jump in small page size if huge page is enabled on the ramblock.  IOW, it's
> destined that only the 1st 4K page will be valid, when unqueue the 2nd+ time
> we'll notice the whole huge page has already been sent anyway.  Switching to
> operating on huge page reduces a lot of the loops of redundant unqueue_page().
>
> Meanwhile, drop the dirty check.  It's not helpful to call test_bit() every
> time to jump over clean pages, as ram_save_host_page() has already done so,
> while in a faster way (see commit ba1b7c812c ("migration/ram: Optimize
> ram_save_host_page()", 2021-05-13)).  So that's not necessary too.
>
> Drop the two tracepoints along the way - based on above analysis it's very
> possible that no one is really using it..
>
> Signed-off-by: Peter Xu <peterx@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

queued.

I added the extra tracepoint that you added later.