From: Paolo Bonzini <pbonzini@redhat.com>
To: qemu-devel@nongnu.org
Cc: Vincenzo Maffione <v.maffione@gmail.com>, mst@redhat.com
Subject: [Qemu-devel] [PATCH 10/10] virtio: combine write of an entry into used ring
Date: Fri, 15 Jan 2016 13:41:58 +0100 [thread overview]
Message-ID: <1452861718-25806-11-git-send-email-pbonzini@redhat.com> (raw)
In-Reply-To: <1452861718-25806-1-git-send-email-pbonzini@redhat.com>
From: Vincenzo Maffione <v.maffione@gmail.com>
Fill in an element of the used ring with a single combined access to the
guest physical memory, rather than using two separated accesses.
This reduces the overhead due to expensive address translation.
Signed-off-by: Vincenzo Maffione <v.maffione@gmail.com>
Message-Id: <e4a89a767a4a92cbb6bcc551e151487eb36e1722.1450218353.git.v.maffione@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
hw/virtio/virtio.c | 25 ++++++++++++-------------
1 file changed, 12 insertions(+), 13 deletions(-)
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 01142da..96bd420 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -153,18 +153,15 @@ static inline uint16_t vring_get_used_event(VirtQueue *vq)
return vring_avail_ring(vq, vq->vring.num);
}
-static inline void vring_used_ring_id(VirtQueue *vq, int i, uint32_t val)
+static inline void vring_used_write(VirtQueue *vq, VRingUsedElem *uelem,
+ int i)
{
hwaddr pa;
- pa = vq->vring.used + offsetof(VRingUsed, ring[i].id);
- virtio_stl_phys(vq->vdev, pa, val);
-}
-
-static inline void vring_used_ring_len(VirtQueue *vq, int i, uint32_t val)
-{
- hwaddr pa;
- pa = vq->vring.used + offsetof(VRingUsed, ring[i].len);
- virtio_stl_phys(vq->vdev, pa, val);
+ virtio_tswap32s(vq->vdev, &uelem->id);
+ virtio_tswap32s(vq->vdev, &uelem->len);
+ pa = vq->vring.used + offsetof(VRingUsed, ring[i]);
+ address_space_write(&address_space_memory, pa, MEMTXATTRS_UNSPECIFIED,
+ (void *)uelem, sizeof(VRingUsedElem));
}
static uint16_t vring_used_idx(VirtQueue *vq)
@@ -273,15 +270,17 @@ void virtqueue_discard(VirtQueue *vq, const VirtQueueElement *elem,
void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
unsigned int len, unsigned int idx)
{
+ VRingUsedElem uelem;
+
trace_virtqueue_fill(vq, elem, len, idx);
virtqueue_unmap_sg(vq, elem, len);
idx = (idx + vq->used_idx) % vq->vring.num;
- /* Get a pointer to the next entry in the used ring. */
- vring_used_ring_id(vq, idx, elem->index);
- vring_used_ring_len(vq, idx, len);
+ uelem.id = elem->index;
+ uelem.len = len;
+ vring_used_write(vq, &uelem, idx);
}
void virtqueue_flush(VirtQueue *vq, unsigned int count)
--
2.5.0
next prev parent reply other threads:[~2016-01-15 12:42 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-15 12:41 [Qemu-devel] [PATCH 00/10] virtio/vring: optimization patches Paolo Bonzini
2016-01-15 12:41 ` [Qemu-devel] [PATCH 01/10] virtio: move VirtQueueElement at the beginning of the structs Paolo Bonzini
2016-01-19 12:09 ` Cornelia Huck
2016-01-19 13:22 ` Paolo Bonzini
2016-01-19 14:01 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 02/10] virtio: move allocation to virtqueue_pop/vring_pop Paolo Bonzini
2016-01-19 12:22 ` Cornelia Huck
2016-01-19 13:16 ` Paolo Bonzini
2016-01-15 12:41 ` [Qemu-devel] [PATCH 03/10] virtio: introduce qemu_get/put_virtqueue_element Paolo Bonzini
2016-01-19 12:30 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 04/10] virtio: introduce virtqueue_alloc_element Paolo Bonzini
2016-01-19 12:40 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 05/10] virtio: slim down allocation of VirtQueueElements Paolo Bonzini
2016-01-19 15:54 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 06/10] vring: " Paolo Bonzini
2016-01-19 15:58 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 07/10] virtio: combine the read of a descriptor Paolo Bonzini
2016-01-19 16:07 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 08/10] virtio: cache used_idx in a VirtQueue field Paolo Bonzini
2016-01-19 16:11 ` Cornelia Huck
2016-01-15 12:41 ` [Qemu-devel] [PATCH 09/10] virtio: read avail_idx from VQ only when necessary Paolo Bonzini
2016-01-19 16:20 ` Cornelia Huck
2016-01-19 16:54 ` Michael S. Tsirkin
2016-01-19 18:48 ` Paolo Bonzini
2016-01-20 17:32 ` Cornelia Huck
2016-01-21 21:40 ` Vincenzo Maffione
2016-01-15 12:41 ` Paolo Bonzini [this message]
2016-01-19 16:26 ` [Qemu-devel] [PATCH 10/10] virtio: combine write of an entry into used ring Cornelia Huck
2016-01-31 10:28 [Qemu-devel] [PATCH v2 00/10] virtio/vring: optimization patches Paolo Bonzini
2016-01-31 10:29 ` [Qemu-devel] [PATCH 10/10] virtio: combine write of an entry into used ring Paolo Bonzini
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