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由 Christoph Lameter 提交于
page-allocator: use integer fields lookup for gfp_zone and check for errors in flags passed to the page allocator This simplifies the code in gfp_zone() and also keeps the ability of the compiler to use constant folding to get rid of gfp_zone processing. The lookup of the zone is done using a bitfield stored in an integer. So the code in gfp_zone is a simple extraction of bits from a constant bitfield. The compiler is generating a load of a constant into a register and then performs a shift and mask operation to get the zone from a gfp_t. No cachelines are touched and no branches have to be predicted by the compiler. We are doing some macro tricks here to convince the compiler to always do the constant folding if possible. Signed-off-by: NChristoph Lameter <cl@linux-foundation.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Reviewed-by: NMel Gorman <mel@csn.ul.ie> Cc: Nick Piggin <nickpiggin@yahoo.com.au> Signed-off-by: NAndrew Morton <akpm@linux-foundation.org> Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>
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