On Tue, Oct 25, 2011 at 3:18 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote: > On Tue, 25 Oct 2011, Mel Gorman wrote: > >> That said, it will be difficult to remember why checking __GFP_NOFAIL in >> this case is necessary and someone might "optimitise" it away later. It >> would be preferable if it was self-documenting. Maybe something like >> this? (This is totally untested) >> > > __GFP_NOFAIL _should_ be optimized away in this case because all he's > passing is __GFP_WAIT | __GFP_NOFAIL. That doesn't make any sense unless > all you want to do is livelock. __GFP_NOFAIL is not set in the case that I care about. If my change is hit, no forward progress has been made, so I agree it should not honor __GFP_NOFAIL. > __GFP_NOFAIL doesn't mean the page allocator would infinitely loop in all > conditions. That's why GFP_ATOMIC | __GFP_NOFAIL actually fails, and I > would argue that __GFP_WAIT | __GFP_NOFAIL should fail as well since it's > the exact same condition except doesn't have access to the extra memory > reserves. > > Suspend needs to either set __GFP_NORETRY to avoid the livelock if it's > going to disable all means of memory reclaiming or freeing in the page > allocator. Or, better yet, just make it GFP_NOWAIT. > It would be nice to give compaction and the slab shrinker a chance to recover a few pages, both methods will work fine in suspend. GFP_NOWAIT will prevent them from ever running, and __GFP_NORETRY will give up even if they are making progress but haven't recovered enough pages. Converting suspend to GFP_NOWAIT would simply be ~GFP_KERNEL instead of ~GFP_IOFS in pm_restrict_gfp_mask(). -- 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