path: root/mm/sparse-vmemmap.c
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authorMichal Hocko <>2017-07-12 14:36:42 -0700
committerLinus Torvalds <>2017-07-12 16:26:03 -0700
commit473738eb78c3e379d682fb8a3cf7e1d17beded9f (patch)
treeb922f4b108a9951b2863ee24b8dc46946a43ebb8 /mm/sparse-vmemmap.c
parent0a782dc31f4d867921eb7caf1f4bb1222e45bb0e (diff)
MIPS: do not use __GFP_REPEAT for order-0 request
Patch series "mm: give __GFP_REPEAT a better semantic". The main motivation for the change is that the current implementation of __GFP_REPEAT is not very much useful. The documentation says: * __GFP_REPEAT: Try hard to allocate the memory, but the allocation attempt * _might_ fail. This depends upon the particular VM implementation. It just fails to mention that this is true only for large (costly) high order which has been the case since the flag was introduced. A similar semantic would be really helpful for smal orders as well, though, because we have places where a failure with a specific fallback error handling is preferred to a potential endless loop inside the page allocator. The earlier cleanup dropped __GFP_REPEAT usage for low (!costly) order users so only those which might use larger orders have stayed. One new user added in the meantime is addressed in patch 1. Let's rename the flag to something more verbose and use it for existing users. Semantic for those will not change. Then implement low (!costly) orders failure path which is hit after the page allocator is about to invoke the oom killer. With that we have a good counterpart for __GFP_NORETRY and finally can tell try as hard as possible without the OOM killer. Xfs code already has an existing annotation for allocations which are allowed to fail and we can trivially map them to the new gfp flag because it will provide the semantic KM_MAYFAIL wants. Christoph didn't consider the new flag really necessary but didn't respond to the OOM killer aspect of the change so I have kept the patch. If this is still seen as not really needed I can drop the patch. kvmalloc will allow also !costly high order allocations to retry hard before falling back to the vmalloc. drm/i915 asked for the new semantic explicitly. Memory migration code, especially for the memory hotplug, should back off rather than invoking the OOM killer as well. This patch (of 6): Commit 3377e227af44 ("MIPS: Add 48-bit VA space (and 4-level page tables) for 4K pages.") has added a new __GFP_REPEAT user but using this flag doesn't really make any sense for order-0 request which is the case here because PUD_ORDER is 0. __GFP_REPEAT has historically effect only on allocation requests with order > PAGE_ALLOC_COSTLY_ORDER. This doesn't introduce any functional change. This is a preparatory patch for later work which renames the flag and redefines its semantic. Link: Signed-off-by: Michal Hocko <> Acked-by: Vlastimil Babka <> Cc: Alex Belits <> Cc: David Daney <> Cc: Ralf Baechle <> Cc: Johannes Weiner <> Cc: Mel Gorman <> Cc: NeilBrown <> Cc: Christoph Hellwig <> Cc: Chris Wilson <> Cc: Darrick J. Wong <> Signed-off-by: Andrew Morton <> Signed-off-by: Linus Torvalds <>
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