virtio: add inorder option
skips ring accesses but drops out of order support Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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parent
2dcd0af568
commit
ce10c1b950
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@ -1,6 +1,6 @@
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all:
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all: ring virtio_ring_0_9 virtio_ring_poll
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all: ring virtio_ring_0_9 virtio_ring_poll virtio_ring_inorder
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CFLAGS += -Wall
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CFLAGS += -pthread -O2 -ggdb
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@ -10,13 +10,16 @@ main.o: main.c main.h
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ring.o: ring.c main.h
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virtio_ring_0_9.o: virtio_ring_0_9.c main.h
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virtio_ring_poll.o: virtio_ring_poll.c virtio_ring_0_9.c main.h
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virtio_ring_inorder.o: virtio_ring_inorder.c virtio_ring_0_9.c main.h
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ring: ring.o main.o
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virtio_ring_0_9: virtio_ring_0_9.o main.o
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virtio_ring_poll: virtio_ring_poll.o main.o
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virtio_ring_inorder: virtio_ring_inorder.o main.o
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clean:
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-rm main.o
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-rm ring.o ring
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-rm virtio_ring_0_9.o virtio_ring_0_9
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-rm virtio_ring_poll.o virtio_ring_poll
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-rm virtio_ring_inorder.o virtio_ring_inorder
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.PHONY: all clean
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@ -26,6 +26,14 @@ struct vring ring;
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* high bits of ring id ^ 0x8000).
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*/
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/* #ifdef RING_POLL */
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/* enabling the below activates experimental in-order code
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* (which skips ring updates and reads and writes len in descriptor).
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*/
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/* #ifdef INORDER */
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#if defined(RING_POLL) && defined(INORDER)
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#error "RING_POLL and INORDER are mutually exclusive"
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#endif
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/* how much padding is needed to avoid false cache sharing */
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#define HOST_GUEST_PADDING 0x80
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@ -35,7 +43,11 @@ struct guest {
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unsigned short last_used_idx;
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unsigned short num_free;
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unsigned short kicked_avail_idx;
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#ifndef INORDER
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unsigned short free_head;
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#else
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unsigned short reserved_free_head;
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#endif
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unsigned char reserved[HOST_GUEST_PADDING - 10];
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} guest;
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@ -66,8 +78,10 @@ void alloc_ring(void)
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guest.avail_idx = 0;
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guest.kicked_avail_idx = -1;
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guest.last_used_idx = 0;
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#ifndef INORDER
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/* Put everything in free lists. */
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guest.free_head = 0;
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#endif
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for (i = 0; i < ring_size - 1; i++)
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ring.desc[i].next = i + 1;
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host.used_idx = 0;
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@ -84,13 +98,20 @@ void alloc_ring(void)
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/* guest side */
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int add_inbuf(unsigned len, void *buf, void *datap)
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{
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unsigned head, avail;
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unsigned head;
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#ifndef INORDER
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unsigned avail;
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#endif
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struct vring_desc *desc;
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if (!guest.num_free)
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return -1;
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#ifdef INORDER
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head = (ring_size - 1) & (guest.avail_idx++);
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#else
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head = guest.free_head;
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#endif
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guest.num_free--;
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desc = ring.desc;
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@ -102,7 +123,9 @@ int add_inbuf(unsigned len, void *buf, void *datap)
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* descriptors.
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*/
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desc[head].flags &= ~VRING_DESC_F_NEXT;
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#ifndef INORDER
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guest.free_head = desc[head].next;
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#endif
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data[head].data = datap;
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@ -113,8 +136,12 @@ int add_inbuf(unsigned len, void *buf, void *datap)
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ring.avail->ring[avail & (ring_size - 1)] =
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(head | (avail & ~(ring_size - 1))) ^ 0x8000;
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#else
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#ifndef INORDER
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/* Barrier A (for pairing) */
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smp_release();
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avail = (ring_size - 1) & (guest.avail_idx++);
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ring.avail->ring[avail] = head;
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#endif
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/* Barrier A (for pairing) */
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smp_release();
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#endif
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@ -141,15 +168,27 @@ void *get_buf(unsigned *lenp, void **bufp)
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return NULL;
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/* Barrier B (for pairing) */
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smp_acquire();
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#ifdef INORDER
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head = (ring_size - 1) & guest.last_used_idx;
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index = head;
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#else
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head = (ring_size - 1) & guest.last_used_idx;
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index = ring.used->ring[head].id;
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#endif
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#endif
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#ifdef INORDER
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*lenp = ring.desc[index].len;
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#else
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*lenp = ring.used->ring[head].len;
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#endif
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datap = data[index].data;
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*bufp = (void*)(unsigned long)ring.desc[index].addr;
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data[index].data = NULL;
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#ifndef INORDER
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ring.desc[index].next = guest.free_head;
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guest.free_head = index;
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#endif
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guest.num_free++;
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guest.last_used_idx++;
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return datap;
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@ -283,16 +322,24 @@ bool use_buf(unsigned *lenp, void **bufp)
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smp_acquire();
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used_idx &= ring_size - 1;
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#ifdef INORDER
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head = used_idx;
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#else
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head = ring.avail->ring[used_idx];
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#endif
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desc = &ring.desc[head];
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#endif
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*lenp = desc->len;
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*bufp = (void *)(unsigned long)desc->addr;
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#ifdef INORDER
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desc->len = desc->len - 1;
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#else
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/* now update used ring */
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ring.used->ring[used_idx].id = head;
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ring.used->ring[used_idx].len = desc->len - 1;
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#endif
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/* Barrier B (for pairing) */
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smp_release();
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host.used_idx++;
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@ -0,0 +1,2 @@
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#define INORDER 1
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#include "virtio_ring_0_9.c"
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