[PATCH 14/14] vmbus: replace modulus operation with subtraction
From: Stephen Hemminger <stephen@networkplumber.org>
Date: 2017-02-01 16:29:01
Subsystem:
hyper-v/azure core and drivers, the rest · Maintainers:
"K. Y. Srinivasan", Haiyang Zhang, Wei Liu, Dexuan Cui, Long Li, Linus Torvalds
Takes less clock cycles to check for ring wrap and subtract than to do a modulus instruction. Signed-off-by: Stephen Hemminger <redacted> --- drivers/hv/ring_buffer.c | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-)
diff --git a/drivers/hv/ring_buffer.c b/drivers/hv/ring_buffer.c
index ee3e488d9dee..8ab6298fd5ae 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c@@ -112,7 +112,8 @@ hv_get_next_readlocation_withoffset(const struct hv_ring_buffer_info *ring_info, u32 next = ring_info->ring_buffer->read_index; next += offset; - next %= ring_info->ring_datasize; + if (next >= ring_info->ring_datasize) + next -= ring_info->ring_datasize; return next; }
@@ -156,7 +157,8 @@ static u32 hv_copyfrom_ringbuffer( memcpy(dest, ring_buffer + start_read_offset, destlen); start_read_offset += destlen; - start_read_offset %= ring_buffer_size; + if (start_read_offset >= ring_buffer_size) + start_read_offset -= ring_buffer_size; return start_read_offset; }
@@ -178,7 +180,8 @@ static u32 hv_copyto_ringbuffer( memcpy(ring_buffer + start_write_offset, src, srclen); start_write_offset += srclen; - start_write_offset %= ring_buffer_size; + if (start_write_offset >= ring_buffer_size) + start_write_offset -= ring_buffer_size; return start_write_offset; }
--
2.11.0