Messages in this thread | | | Date | Sat, 26 Feb 2011 01:16:11 +0100 | From | Andrea Arcangeli <> | Subject | Re: [PATCH 2/2] mm: compaction: Minimise the time IRQs are disabled while isolating pages for migration |
| |
On Fri, Feb 25, 2011 at 11:32:04PM +0100, Johannes Weiner wrote: > I don't understand why this conditional is broken up like this. > cond_resched() will have the right checks anyway. Okay, you would > save fatal_signal_pending() in the 'did one cluster' case. Is it that > expensive? Couldn't this be simpler like > > did_cluster = ((low_pfn + 1) % SWAP_CLUSTER_MAX) == 0 > lock_contended = spin_is_contended(&zone->lru_lock); > if (did_cluster || lock_contended || need_resched()) { > spin_unlock_irq(&zone->lru_lock); > cond_resched(); > spin_lock_irq(&zone->lru_lock); > if (fatal_signal_pending(current)) > break; > } > > instead?
If we don't release irqs first, how can need_resched get set in the first place if the local apic irq can't run? I guess that's why there's no cond_resched_lock_irq. BTW, I never liked too much clearing interrupts for locks that can't ever be taken from irq (it's a scalability boost to reduce contention but it makes things like above confusing and it increases irq latency a bit.
| |