Re: [PATCH] migration: only migrate_prep() once per move_pages()

[Christoph Lameter]

On Wed, 15 Apr 2009, Brice Goglin wrote:

> But lru_add_drain_all() touches some code that I am far from
> understanding :/ Can we imagine using IPI instead of a deferred
> work_struct for this kind of things? Or maybe, for each processor, check
> whether drain_cpu_pagevecs() would have something to do before actually
> scheduling the local work_struct? It's racy, but migrate_prep() doesn't
> guarantee anyway that pages won't be moved out of the LRU before the
> actual migration, so...

IPI means that code must run with interrupts disabled.

> > BTW, current users of sys_move_pages() does retry when it gets -EBUSY ?
> >
>
> I'd say they ignore it since it doesn't happen often :)

Right.

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