Commit 2fddfdb5 authored by Asias He's avatar Asias He Committed by Will Deacon
Browse files

kvm tools: Improve virtio blk request processing



There are at most bdev->reqs[VIRTIO_BLK_QUEUE_SIZE] outstanding requests
at any time.  We can simply use the head of each request to fetch the
right 'struct blk_dev_req' in bdev->reqs[].

So, we can eliminate the list and lock operations which introduced by
virtio_blk_req_{pop, push}.

Signed-off-by: default avatarAsias He <asias.hejun@gmail.com>
Signed-off-by: default avatarPekka Enberg <penberg@kernel.org>
parent d951bae0
......@@ -58,7 +58,8 @@ static inline void *guest_pfn_to_host(struct kvm *kvm, u32 pfn)
struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32 head, u32 len);
bool virtio_queue__should_signal(struct virt_queue *vq);
u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
u16 virt_queue__get_iov(struct virt_queue *vq, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm);
u16 virt_queue__get_head_iov(struct virt_queue *vq, struct iovec iov[], u16 *out, u16 *in, u16 head, struct kvm *kvm);
u16 virt_queue__get_inout_iov(struct kvm *kvm, struct virt_queue *queue,
struct iovec in_iov[], struct iovec out_iov[],
u16 *in, u16 *out);
......
......@@ -30,7 +30,6 @@
#define NUM_VIRT_QUEUES 1
struct blk_dev_req {
struct list_head list;
struct virt_queue *vq;
struct blk_dev *bdev;
struct iovec iov[VIRTIO_BLK_QUEUE_SIZE];
......@@ -57,27 +56,6 @@ struct blk_dev {
static LIST_HEAD(bdevs);
static int compat_id;
static struct blk_dev_req *virtio_blk_req_pop(struct blk_dev *bdev)
{
struct blk_dev_req *req = NULL;
mutex_lock(&bdev->req_mutex);
if (!list_empty(&bdev->req_list)) {
req = list_first_entry(&bdev->req_list, struct blk_dev_req, list);
list_del_init(&req->list);
}
mutex_unlock(&bdev->req_mutex);
return req;
}
static void virtio_blk_req_push(struct blk_dev *bdev, struct blk_dev_req *req)
{
mutex_lock(&bdev->req_mutex);
list_add(&req->list, &bdev->req_list);
mutex_unlock(&bdev->req_mutex);
}
void virtio_blk_complete(void *param, long len)
{
struct blk_dev_req *req = param;
......@@ -95,8 +73,6 @@ void virtio_blk_complete(void *param, long len)
if (virtio_queue__should_signal(&bdev->vqs[queueid]))
bdev->vtrans.trans_ops->signal_vq(req->kvm, &bdev->vtrans, queueid);
virtio_blk_req_push(req->bdev, req);
}
static void virtio_blk_do_io_request(struct kvm *kvm, struct blk_dev_req *req)
......@@ -141,15 +117,14 @@ static void virtio_blk_do_io_request(struct kvm *kvm, struct blk_dev_req *req)
static void virtio_blk_do_io(struct kvm *kvm, struct virt_queue *vq, struct blk_dev *bdev)
{
while (virt_queue__available(vq)) {
struct blk_dev_req *req = virtio_blk_req_pop(bdev);
struct blk_dev_req *req;
u16 head;
*req = (struct blk_dev_req) {
.vq = vq,
.bdev = bdev,
.kvm = kvm,
};
req->head = virt_queue__get_iov(vq, req->iov, &req->out, &req->in, kvm);
while (virt_queue__available(vq)) {
head = virt_queue__pop(vq);
req = &bdev->reqs[head];
req->head = virt_queue__get_head_iov(vq, req->iov, &req->out, &req->in, head, kvm);
req->vq = vq;
virtio_blk_do_io_request(kvm, req);
}
......@@ -235,7 +210,7 @@ static struct virtio_ops blk_dev_virtio_ops = (struct virtio_ops) {
void virtio_blk__init(struct kvm *kvm, struct disk_image *disk)
{
struct blk_dev *bdev;
size_t i;
unsigned int i;
if (!disk)
return;
......@@ -261,9 +236,10 @@ void virtio_blk__init(struct kvm *kvm, struct disk_image *disk)
list_add_tail(&bdev->list, &bdevs);
INIT_LIST_HEAD(&bdev->req_list);
for (i = 0; i < ARRAY_SIZE(bdev->reqs); i++)
list_add(&bdev->reqs[i].list, &bdev->req_list);
for (i = 0; i < ARRAY_SIZE(bdev->reqs); i++) {
bdev->reqs[i].bdev = bdev;
bdev->reqs[i].kvm = kvm;
}
disk_image__set_callback(bdev->disk, virtio_blk_complete);
......
......@@ -33,18 +33,18 @@ struct vring_used_elem *virt_queue__set_used_elem(struct virt_queue *queue, u32
return used_elem;
}
u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm)
u16 virt_queue__get_head_iov(struct virt_queue *vq, struct iovec iov[], u16 *out, u16 *in, u16 head, struct kvm *kvm)
{
struct vring_desc *desc;
u16 head, idx;
u16 idx;
idx = head = virt_queue__pop(queue);
idx = head;
*out = *in = 0;
do {
desc = virt_queue__get_desc(queue, idx);
iov[*out + *in].iov_base = guest_flat_to_host(kvm, desc->addr);
iov[*out + *in].iov_len = desc->len;
desc = virt_queue__get_desc(vq, idx);
iov[*out + *in].iov_base = guest_flat_to_host(kvm, desc->addr);
iov[*out + *in].iov_len = desc->len;
if (desc->flags & VRING_DESC_F_WRITE)
(*in)++;
else
......@@ -58,13 +58,22 @@ u16 virt_queue__get_iov(struct virt_queue *queue, struct iovec iov[], u16 *out,
return head;
}
u16 virt_queue__get_iov(struct virt_queue *vq, struct iovec iov[], u16 *out, u16 *in, struct kvm *kvm)
{
u16 head;
head = virt_queue__pop(vq);
return virt_queue__get_head_iov(vq, iov, out, in, head, kvm);
}
/* in and out are relative to guest */
u16 virt_queue__get_inout_iov(struct kvm *kvm, struct virt_queue *queue,
struct iovec in_iov[], struct iovec out_iov[],
u16 *in, u16 *out)
{
u16 head, idx;
struct vring_desc *desc;
u16 head, idx;
idx = head = virt_queue__pop(queue);
*out = *in = 0;
......@@ -86,6 +95,7 @@ u16 virt_queue__get_inout_iov(struct kvm *kvm, struct virt_queue *queue,
else
break;
} while (1);
return head;
}
......
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