Re: [PATCH 5/7] mm/page_alloc: Protect PCP lists with a spinlock

[Mel Gorman]

On Mon, Jul 04, 2022 at 02:31:17PM +0200, Vlastimil Babka wrote:
> On 6/24/22 14:54, Mel Gorman wrote:
> > Currently the PCP lists are protected by using local_lock_irqsave to
> > prevent migration and IRQ reentrancy but this is inconvenient.  Remote
> > draining of the lists is impossible and a workqueue is required and every
> > task allocation/free must disable then enable interrupts which is
> > expensive.
> > 
> > As preparation for dealing with both of those problems, protect the lists
> > with a spinlock.  The IRQ-unsafe version of the lock is used because IRQs
> > are already disabled by local_lock_irqsave.  spin_trylock is used in
> > preparation for a time when local_lock could be used instead of
> > lock_lock_irqsave.
> 
>   ^ local_lock_irqsave?
> 

More appropriate given how the series evolved would be;

spin_trylock is used in combination with local_lock_irqsave() but later
will be replaced with a spin_trylock_irqsave when the local_lock is
removed.

-- 
Mel Gorman
SUSE Labs