I've tested Yury Norov's find_bit reimplementation with the test_find_bit module (https://lkml.org/lkml/2015/3/8/141) and measured about 35-40% performance degradation on arm64 3.18 run with fixed CPU frequency. The performance degradation appears to be caused by the helper function _find_next_bit. After inlining this function into find_next_bit and find_next_zero_bit I get slightly better performance than the old implementation: find_next_zero_bit find_next_bit old new inline old new inline 26 36 24 24 33 23 25 36 24 24 33 23 26 36 24 24 33 23 25 36 24 24 33 23 25 36 24 24 33 23 25 37 24 24 33 23 25 37 24 24 33 23 25 37 24 24 33 23 25 36 24 24 33 23 25 37 24 24 33 23 Signed-off-by: Cassidy Burden <cburden@xxxxxxxxxxxxxx> Cc: Alexey Klimov <klimov.linux@xxxxxxxxx> Cc: David S. Miller <davem@xxxxxxxxxxxxx> Cc: Daniel Borkmann <dborkman@xxxxxxxxxx> Cc: Hannes Frederic Sowa <hannes@xxxxxxxxxxxxxxxxxxx> Cc: Lai Jiangshan <laijs@xxxxxxxxxxxxxx> Cc: Mark Salter <msalter@xxxxxxxxxx> Cc: AKASHI Takahiro <takahiro.akashi@xxxxxxxxxx> Cc: Thomas Graf <tgraf@xxxxxxx> Cc: Valentin Rothberg <valentinrothberg@xxxxxxxxx> Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> --- lib/find_bit.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/lib/find_bit.c b/lib/find_bit.c index 18072ea..d0e04f9 100644 --- a/lib/find_bit.c +++ b/lib/find_bit.c @@ -28,7 +28,7 @@ * find_next_zero_bit. The difference is the "invert" argument, which * is XORed with each fetched word before searching it for one bits. */ -static unsigned long _find_next_bit(const unsigned long *addr, +static inline unsigned long _find_next_bit(const unsigned long *addr, unsigned long nbits, unsigned long start, unsigned long invert) { unsigned long tmp; -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project -- To unsubscribe from this list: send the line "unsubscribe linux-arm-msm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
