On Wed, Oct 26, 2011 at 12:22:14AM -0700, Colin Cross wrote: > On Wed, Oct 26, 2011 at 12:10 AM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > > On Tue, 25 Oct 2011, Colin Cross wrote: > > > >> > gfp_allowed_mask is initialized to GFP_BOOT_MASK to start so that __GFP_FS > >> > is never allowed before the slab allocator is completely initialized, so > >> > you've now implicitly made all early boot allocations to be __GFP_NORETRY > >> > even though they may not pass it. > >> > >> Only before interrupts are enabled, and then isn't it vulnerable to > >> the same livelock? Interrupts are off, single cpu, kswapd can't run. > >> If an allocation ever failed, which seems unlikely, why would retrying > >> help? > >> > > > > If you want to claim gfp_allowed_mask as a pm-only entity, then I see no > > problem with this approach. However, if gfp_allowed_mask would be allowed > > to temporarily change after init for another purpose then it would make > > sense to retry because another allocation with __GFP_FS on another cpu or > > kswapd could start making progress could allow for future memory freeing. > > > > The suggestion to add a hook directly into a pm-interface was so that we > > could isolate it only to suspend and, to me, is the most maintainable > > solution. > > > > pm_restrict_gfp_mask seems to claim gfp_allowed_mask as owned by pm at runtime: > "gfp_allowed_mask also should only be modified with pm_mutex held, > unless the suspend/hibernate code is guaranteed not to run in parallel > with that modification" > > I think we've wrapped around to Mel's original patch, which adds a > pm_suspending() helper that is implemented next to > pm_restrict_gfp_mask. His patch puts the check inside > !did_some_progress instead of should_alloc_retry, which I prefer as it > at least keeps trying until reclaim isn't working. Pekka was trying > to avoid adding pm-specific checks into the allocator, which is why I > stuck to the symptom (__GFP_FS is clear) rather than the cause (PM). > Right now, I'm still no seeing a problem with the pm_suspending() check as it's made for a corner-case situation in a very slow path that is self-documenting. This thread has died somewhat and there is still no fix merged. Is someone cooking up a patch they would prefer as an alternative? If not, I'm going to resubmit the fix based on pm_suspending. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>