On Thu 14-04-16 12:56:28, David Rientjes wrote: > On Mon, 11 Apr 2016, Michal Hocko wrote: > > > From: Michal Hocko <mhocko@xxxxxxxx> > > > > __GFP_REPEAT has a rather weak semantic but since it has been introduced > > around 2.6.12 it has been ignored for low order allocations. Yet we have > > the full kernel tree with its usage for apparently order-0 allocations. > > This is really confusing because __GFP_REPEAT is explicitly documented > > to allow allocation failures which is a weaker semantic than the current > > order-0 has (basically nofail). > > > > Let's simply drop __GFP_REPEAT from those places. This would allow > > to identify place which really need allocator to retry harder and > > formulate a more specific semantic for what the flag is supposed to do > > actually. > > > > Cc: linux-arch@xxxxxxxxxxxxxxx > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > > I did exactly this before, and Andrew objected saying that __GFP_REPEAT > may not be needed for the current page allocator's implementation but > could with others and that setting __GFP_REPEAT for an allocation > provided useful information with regards to intent. >From what I've seen it was more a copy&paste of the arch code which spread out this flag and there was also a misleading usage. > At the time, I attempted to eliminate __GFP_REPEAT entirely. This is not my plan. I actually want to provide a useful semantic for something like this flag - aka try really hard but eventually fail for all orders and stop being special only for those that are costly. I will call it __GFP_BEST_EFFORT. But I have to clean up the current usage first. Costly orders will keep __GFP_REPEAT because the intent is clear there. All others will lose the flag and then we can start adding __GFP_BEST_EFFORT where it matters also for lower orders. -- Michal Hocko SUSE Labs -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
