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authorDavid Howells <dhowells@redhat.com>2009-05-06 16:03:03 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2009-05-06 16:36:10 -0700
commit3a6be87fd1e5cdbbc3b6a14d02a3efa9ecba1d3f (patch)
treebb58ea44178d8a16861d445df8fa3623ddf02d38 /mm/Kconfig
parent9155203a5de94278525647b16733f0c315f3b786 (diff)
nommu: clamp zone_batchsize() to 0 under NOMMU conditions
Clamp zone_batchsize() to 0 under NOMMU conditions to stop free_hot_cold_page() from queueing and batching frees. The problem is that under NOMMU conditions it is really important to be able to allocate large contiguous chunks of memory, but when munmap() or exit_mmap() releases big stretches of memory, return of these to the buddy allocator can be deferred, and when it does finally happen, it can be in small chunks. Whilst the fragmentation this incurs isn't so much of a problem under MMU conditions as userspace VM is glued together from individual pages with the aid of the MMU, it is a real problem if there isn't an MMU. By clamping the page freeing queue size to 0, pages are returned to the allocator immediately, and the buddy detector is more likely to be able to glue them together into large chunks immediately, and fragmentation is less likely to occur. By disabling batching of frees, and by turning off the trimming of excess space during boot, Coldfire can manage to boot. Reported-by: Lanttor Guo <lanttor.guo@freescale.com> Signed-off-by: David Howells <dhowells@redhat.com> Tested-by: Lanttor Guo <lanttor.guo@freescale.com> Cc: Greg Ungerer <gerg@snapgear.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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