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Date: Tue, 25 Aug 2020 14:53:07 +0000 From: David Laight <David.Laight@...LAB.COM> To: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "'linux-sctp@...r.kernel.org'" <linux-sctp@...r.kernel.org>, Eric Biggers <ebiggers@...nel.org>, 'Marcelo Ricardo Leitner' <marcelo.leitner@...il.com>, 'Catalin Marinas' <catalin.marinas@....com>, "'kent.overstreet@...il.com'" <kent.overstreet@...il.com>, Andrew Morton <akpm@...ux-foundation.org>, "'Neil Horman'" <nhorman@...driver.com> Subject: [PATCH 02/13] lib/generic-radix-tree: Optimise out ilog2(variable). ilog2() is relatively expensive (especially without bit-scan instructions). Replace the comparisons 'ilog2(x) >= y' with '(x >> y) != 0'. Signed-off-by: David Laight <david.laight@...lab.com> --- lib/generic-radix-tree.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/lib/generic-radix-tree.c b/lib/generic-radix-tree.c index 5695fe547f9d..d5e97b51308d 100644 --- a/lib/generic-radix-tree.c +++ b/lib/generic-radix-tree.c @@ -57,7 +57,7 @@ void *__genradix_ptr(struct __genradix *radix, size_t offset) struct genradix_node *n = genradix_root_to_node(r); unsigned level = genradix_root_to_depth(r); - if (ilog2(offset) >= genradix_depth_shift(level)) + if (offset >> genradix_depth_shift(level)) return NULL; while (1) { @@ -115,7 +115,7 @@ void *__genradix_ptr_alloc(struct __genradix *radix, size_t offset, n = genradix_root_to_node(r); level = genradix_root_to_depth(r); - if (n && ilog2(offset) < genradix_depth_shift(level)) + if (n && !(offset >> genradix_depth_shift(level))) break; new_node = genradix_alloc_node(gfp_mask); @@ -171,7 +171,7 @@ void *__genradix_iter_peek(struct genradix_iter *iter, n = genradix_root_to_node(r); level = genradix_root_to_depth(r); - if (ilog2(iter->offset) >= genradix_depth_shift(level)) + if (iter->offset >> genradix_depth_shift(level)) return NULL; while (level) { -- 2.25.1 - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
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