From: Long Li <lon...@microsoft.com>
The ring buffer code uses %= to calculate index. For x86/64, %= compiles to
div, more than 10 times slower than sub.
Replace div with sub for this data heavy code path.
Signed-off-by: Long Li <lon...@microsoft.com>
---
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 cd49cb1..f8eee6e 100644
--- a/drivers/hv/ring_buffer.c
+++ b/drivers/hv/ring_buffer.c
@@ -135,7 +135,8 @@ hv_get_next_readlocation_withoffset(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;
}
@@ -179,7 +180,8 @@ 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;
}
@@ -201,7 +203,8 @@ 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;
}
--
2.7.4
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