Messages in this thread Patch in this message | | | From | Rakib Mullick <> | Subject | [PATCH] lib: Avoid redundant sizeof checking in __bitmap_weight() calculation. | Date | Tue, 14 Nov 2017 12:57:31 +0600 |
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Currently, during __bitmap_weight() calculation hweight_long() is used. Inside a hweight_long() a check has been made to figure out whether a hweight32() or hweight64() version to use.
However, it's unnecessary to do it in case of __bitmap_weight() calculation inside the loop. We can detect whether to use hweight32() or hweight64() upfront and call respective function directly. It also reduces the vmlinux size.
Before the patch: text data bss dec hex filename 12901332 7798930 14541816 35242078 219c05e vmlinux
After the patch: text data bss dec hex filename 12901331 7798930 14541816 35242077 219c05d vmlinux
Signed-off-by: Rakib Mullick <rakib.mullick@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk> Cc: Matthew Wilcox <mawilcox@microsoft.com> Cc: Yury Norov <ynorov@caviumnetworks.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org>
--- Patch was created against torvald's tree (commit 43ff2f4db9d0f764).
lib/bitmap.c | 13 +++++++++---- 1 file changed, 9 insertions(+), 4 deletions(-)
diff --git a/lib/bitmap.c b/lib/bitmap.c index d8f0c09..552096f 100644 --- a/lib/bitmap.c +++ b/lib/bitmap.c @@ -241,10 +241,15 @@ EXPORT_SYMBOL(__bitmap_subset); int __bitmap_weight(const unsigned long *bitmap, unsigned int bits) { unsigned int k, lim = bits/BITS_PER_LONG; - int w = 0; - - for (k = 0; k < lim; k++) - w += hweight_long(bitmap[k]); + int w = 0, is32 = sizeof(bitmap[0]) ? 1 : 0; + + if (is32) { + for (k = 0; k < lim; k++) + w += hweight32(bitmap[k]); + } else { + for (k = 0; k < lim; k++) + w += hweight64(bitmap[k]); + } if (bits % BITS_PER_LONG) w += hweight_long(bitmap[k] & BITMAP_LAST_WORD_MASK(bits)); -- 2.9.3
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