On Thu, 12 Nov 2015, mhocko@xxxxxxxxxx wrote: > From: Michal Hocko <mhocko@xxxxxxxx> > > __alloc_pages_high_priority doesn't do anything special other than it > calls get_page_from_freelist and loops around GFP_NOFAIL allocation > until it succeeds. It would be better if the first part was done in > __alloc_pages_slowpath where we modify the zonelist because this would > be easier to read and understand. And do the retry at the very same > place because retrying without even attempting to do any reclaim is > fragile because we are basically relying on somebody else to make the > reclaim (be it the direct reclaim or OOM killer) for us. The caller > might be holding resources (e.g. locks) which block other other > reclaimers from making any progress for example. > > Remove the helper and open code it into its only user. We have to be > careful about __GFP_NOFAIL allocations from the PF_MEMALLOC context > even though this is a very bad idea to begin with because no progress > can be gurateed at all. We shouldn't break the __GFP_NOFAIL semantic > here though. It could be argued that this is essentially GFP_NOWAIT > context which we do not support but PF_MEMALLOC is much harder to check > for existing users because they might happen deep down the code path > performed much later after setting the flag so we cannot really rule out > there is no kernel path triggering this combination. > > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > --- > > Hi, > I think that this is more a cleanup than any functional change. We > are rarely screwed so much that __alloc_pages_high_priority would > fail. Yet I think that __alloc_pages_high_priority is obscuring the > overal intention more than it is helpful. Another motivation is to > reduce wait_iff_congested call to a single one in the allocator. I plan > to do other changes in that area and get rid of it altogether. I think it's a combination of a cleanup (the inlining of __alloc_pages_high_priority) and a functional change (no longer looping infinitely around a get_page_from_freelist() call). I'd suggest doing the inlining in one patch and then the reworking of __GFP_NOFAIL when ALLOC_NO_WATERMARKS fails just so we could easily revert the latter if necessary. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>