On Fri, Jun 17, 2022 at 11:39:03AM +0200, Nicolas Saenz Julienne wrote: > Hi Mel, > > On Mon, 2022-06-13 at 13:56 +0100, Mel Gorman wrote: > > @@ -3446,12 +3490,16 @@ void free_unref_page(struct page *page, unsigned int order) > > migratetype = MIGRATE_MOVABLE; > > } > > > > - local_lock_irqsave(&pagesets.lock, flags); > > - freed_pcp = free_unref_page_commit(page, migratetype, order, false); > > - local_unlock_irqrestore(&pagesets.lock, flags); > > - > > - if (unlikely(!freed_pcp)) > > + zone = page_zone(page); > > + pcp_trylock_prepare(UP_flags); > > Now that you're calling the *_irqsave() family of function you can drop > pcp_trylock_prepare/finish() > > For the record in UP: > > #define spin_trylock_irqsave(lock, flags) \ > ({ \ > local_irq_save(flags); \ > 1; > }) > The missing patch that is deferred for a later release uses spin_trylock so unless that is never merged because there is an unfixable flaw in it, I'd prefer to leave the preparation in place. > > + pcp = pcpu_spin_trylock_irqsave(struct per_cpu_pages, lock, zone->per_cpu_pageset, flags); > > + if (pcp) { > > + free_unref_page_commit(pcp, zone, page, migratetype, order); > > + pcp_spin_unlock_irqrestore(pcp, flags); > > + } else { > > free_one_page(page_zone(page), page, pfn, order, migratetype, FPI_NONE); > > + } > > + pcp_trylock_finish(UP_flags); > > } > > > > /* > > As Vlastimil mentioned elsewhere, I also wonder if it makes sense to just > bypass patch #5. Especially as its intent isn't true anymore: > > "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." > It's still true, the patch just isn't included as I wanted them to be separated by time so a bisection that points to it is "obvious" instead of pointing at the whole series as being a potential problem. -- Mel Gorman SUSE Labs