We use inline and get gcc to do the right thing inlining the
"indirect" traversal functions. This also means we don't need to
clean the sgs.
for i in `seq 50`; do /usr/bin/time -f 'Wall time:%e' ./vringh_test --indirect --eventidx --parallel --fast-vringh; done 2>&1 | stats --trim-outliers:
Before:
Using CPUS 0 and 3
Guest: notified 0, pinged 39014-39063(39062)
Host: notified 39014-39063(39062), pinged 0
Wall time:1.900000-2.350000(1.921875)
After:
Using CPUS 0 and 3
Guest: notified 0, pinged 39062-39063(39063)
Host: notified 39062-39063(39063), pinged 0
Wall time:1.760000-2.220000(1.789167)
Signed-off-by: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c
index c537385..a78ad45 100644
--- a/drivers/virtio/virtio_ring.c
+++ b/drivers/virtio/virtio_ring.c
@@ -98,13 +98,31 @@ struct vring_virtqueue
#define to_vvq(_vq) container_of(_vq, struct vring_virtqueue, vq)
+static inline struct scatterlist *sg_next_chained(struct scatterlist *sg,
+ unsigned int *count)
+{
+ return sg_next(sg);
+}
+
+static inline struct scatterlist *sg_next_arr(struct scatterlist *sg,
+ unsigned int *count)
+{
+ if (--(*count) == 0)
+ return NULL;
+ return sg + 1;
+}
+
/* Set up an indirect table of descriptors and add it to the queue. */
-static int vring_add_indirect(struct vring_virtqueue *vq,
- struct scatterlist *sgs[],
- unsigned int total_sg,
- unsigned int out_sgs,
- unsigned int in_sgs,
- gfp_t gfp)
+static inline int vring_add_indirect(struct vring_virtqueue *vq,
+ struct scatterlist *sgs[],
+ struct scatterlist *(*next)
+ (struct scatterlist *, unsigned int *),
+ unsigned int total_sg,
+ unsigned int total_out,
+ unsigned int total_in,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ gfp_t gfp)
{
struct vring_desc *desc;
unsigned head;
@@ -125,7 +143,7 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
/* Transfer entries from the sg lists into the indirect page */
i = 0;
for (n = 0; n < out_sgs; n++) {
- for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+ for (sg = sgs[n]; sg; sg = next(sg, &total_out)) {
desc[i].flags = VRING_DESC_F_NEXT;
desc[i].addr = sg_phys(sg);
desc[i].len = sg->length;
@@ -134,7 +152,7 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
}
}
for (; n < (out_sgs + in_sgs); n++) {
- for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+ for (sg = sgs[n]; sg; sg = next(sg, &total_in)) {
desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
desc[i].addr = sg_phys(sg);
desc[i].len = sg->length;
@@ -163,17 +181,20 @@ static int vring_add_indirect(struct vring_virtqueue *vq,
return head;
}
-static int virtqueue_add(struct virtqueue *_vq,
- struct scatterlist *sgs[],
- unsigned int total_sg,
- unsigned int out_sgs,
- unsigned int in_sgs,
- void *data,
- gfp_t gfp)
+static inline int virtqueue_add(struct virtqueue *_vq,
+ struct scatterlist *sgs[],
+ struct scatterlist *(*next)
+ (struct scatterlist *, unsigned int *),
+ unsigned int total_out,
+ unsigned int total_in,
+ unsigned int out_sgs,
+ unsigned int in_sgs,
+ void *data,
+ gfp_t gfp)
{
struct vring_virtqueue *vq = to_vvq(_vq);
struct scatterlist *sg;
- unsigned int i, n, avail, uninitialized_var(prev);
+ unsigned int i, n, avail, uninitialized_var(prev), total_sg;
int head;
START_USE(vq);
@@ -193,11 +214,14 @@ static int virtqueue_add(struct virtqueue *_vq,
}
#endif
+ total_sg = total_in + total_out;
+
/* If the host supports indirect descriptor tables, and we have multiple
* buffers, then go indirect. FIXME: tune this threshold */
if (vq->indirect && total_sg > 1 && vq->vq.num_free) {
- head = vring_add_indirect(vq, sgs, total_sg, out_sgs, in_sgs,
- gfp);
+ head = vring_add_indirect(vq, sgs, next, total_sg, total_out,
+ total_in,
+ out_sgs, in_sgs, gfp);
if (likely(head >= 0))
goto add_head;
}
@@ -222,7 +246,7 @@ static int virtqueue_add(struct virtqueue *_vq,
head = i = vq->free_head;
for (n = 0; n < out_sgs; n++) {
- for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+ for (sg = sgs[n]; sg; sg = next(sg, &total_out)) {
vq->vring.desc[i].flags = VRING_DESC_F_NEXT;
vq->vring.desc[i].addr = sg_phys(sg);
vq->vring.desc[i].len = sg->length;
@@ -231,7 +255,7 @@ static int virtqueue_add(struct virtqueue *_vq,
}
}
for (; n < (out_sgs + in_sgs); n++) {
- for (sg = sgs[n]; sg; sg = sg_next(sg)) {
+ for (sg = sgs[n]; sg; sg = next(sg, &total_in)) {
vq->vring.desc[i].flags = VRING_DESC_F_NEXT|VRING_DESC_F_WRITE;
vq->vring.desc[i].addr = sg_phys(sg);
vq->vring.desc[i].len = sg->length;
@@ -293,21 +317,12 @@ int virtqueue_add_buf(struct virtqueue *_vq,
gfp_t gfp)
{
struct scatterlist *sgs[2];
- unsigned int i;
sgs[0] = sg;
sgs[1] = sg + out;
- /* Workaround until callers pass well-formed sgs. */
- for (i = 0; i < out + in; i++)
- sg_unmark_end(sg + i);
-
- sg_mark_end(sg + out + in - 1);
- if (out && in)
- sg_mark_end(sg + out - 1);
-
- return virtqueue_add(_vq, sgs, out+in, out ? 1 : 0, in ? 1 : 0,
- data, gfp);
+ return virtqueue_add(_vq, sgs, sg_next_arr,
+ out, in, out ? 1 : 0, in ? 1 : 0, data, gfp);
}
EXPORT_SYMBOL_GPL(virtqueue_add_buf);
@@ -332,15 +347,21 @@ int virtqueue_add_sgs(struct virtqueue *_vq,
void *data,
gfp_t gfp)
{
- unsigned int i, total_sg;
+ unsigned int i, total_out, total_in;
/* Count them first. */
- for (i = total_sg = 0; i < out_sgs + in_sgs; i++) {
+ for (i = total_out = total_in = 0; i < out_sgs; i++) {
+ struct scatterlist *sg;
+ for (sg = sgs[i]; sg; sg = sg_next(sg))
+ total_out++;
+ }
+ for (; i < out_sgs + in_sgs; i++) {
struct scatterlist *sg;
for (sg = sgs[i]; sg; sg = sg_next(sg))
- total_sg++;
+ total_in++;
}
- return virtqueue_add(_vq, sgs, total_sg, out_sgs, in_sgs, data, gfp);
+ return virtqueue_add(_vq, sgs, sg_next_chained,
+ total_out, total_in, out_sgs, in_sgs, data, gfp);
}
EXPORT_SYMBOL_GPL(virtqueue_add_sgs);
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