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Re: [Qemu-devel] [PATCH 07/10] virtio: combine the read of a descriptor
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From: |
Gonglei (Arei) |
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Subject: |
Re: [Qemu-devel] [PATCH 07/10] virtio: combine the read of a descriptor |
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Date: |
Thu, 4 Feb 2016 07:48:08 +0000 |
Hi Paolo,
> From: Paolo Bonzini [mailto:address@hidden On Behalf Of Paolo
> Bonzini
>
> On 03/02/2016 13:34, Gonglei (Arei) wrote:
> > Hi,
> >
> >> Subject: [Qemu-devel] [PATCH 07/10] virtio: combine the read of a
> >> descriptor
> >>
> >> Compared to vring, virtio has a performance penalty of 10%. Fix it
> >> by combining all the reads for a descriptor in a single address_space_read
> >> call. This also simplifies the code nicely.
> >>
> >> Reviewed-by: Cornelia Huck <address@hidden>
> >> Signed-off-by: Paolo Bonzini <address@hidden>
> >> ---
> >> hw/virtio/virtio.c | 86
> >> ++++++++++++++++++++++--------------------------------
> >> 1 file changed, 35 insertions(+), 51 deletions(-)
> >>
> >
> > Unbelievable! After applying this patch, the virtio-crypto speed can attach
> 74MB/sec, host
> > Cpu overhead is 180% (the main thread 100% and vcpu threads 80%)
>
> The three patches from Vincenzo will help too. What was it like before?
>
That's true, and I replied in the cover letter.
> Also, are you using ioeventfd or dataplane? virtio-crypto sounds like
> something that could be very easily run outside the "big QEMU lock".
>
Yes, all testing results based on the conditions of ioeventfd enabled. And I
also realized the virtio-crypto-dataplane scheme, got the below results:
Testing AES-128-CBC cipher:
Encrypting in chunks of 256 bytes: done. 370.81 MiB in 5.02 secs: 73.92
MiB/sec (1518832 packets)
Encrypting in chunks of 256 bytes: done. 374.09 MiB in 5.02 secs: 74.51
MiB/sec (1532272 packets)
Encrypting in chunks of 256 bytes: done. 372.05 MiB in 5.02 secs: 74.11
MiB/sec (1523920 packets)
Encrypting in chunks of 256 bytes: done. 365.77 MiB in 5.02 secs: 72.86
MiB/sec (1498200 packets)
Encrypting in chunks of 256 bytes: done. 379.63 MiB in 5.02 secs: 75.62
MiB/sec (1554976 packets)
Encrypting in chunks of 256 bytes: done. 374.61 MiB in 5.02 secs: 74.62
MiB/sec (1534384 packets)
Encrypting in chunks of 256 bytes: done. 372.13 MiB in 5.02 secs: 74.12
MiB/sec (1524226 packets)
Encrypting in chunks of 256 bytes: done. 374.18 MiB in 5.02 secs: 74.53
MiB/sec (1532656 packets)
11.44% qemu-kvm [.] memory_region_find
6.31% qemu-kvm [.] qemu_get_ram_ptr
4.61% libpthread-2.19.so [.] __pthread_mutex_unlock_usercnt
3.54% qemu-kvm [.] qemu_ram_addr_from_host
2.80% libpthread-2.19.so [.] pthread_mutex_lock
2.55% qemu-kvm [.] object_unref
2.49% libc-2.19.so [.] malloc
2.47% libc-2.19.so [.] _int_malloc
2.34% libc-2.19.so [.] _int_free
2.18% qemu-kvm [.] object_ref
2.18% qemu-kvm [.] address_space_translate
2.03% libc-2.19.so [.] __memcpy_sse2_unaligned
1.76% libc-2.19.so [.] malloc_consolidate
1.56% qemu-kvm [.] addrrange_intersection
1.52% qemu-kvm [.] vring_pop
1.36% qemu-kvm [.] find_next_zero_bit
1.30% [kernel] [k] native_write_msr_safe
1.29% qemu-kvm [.] addrrange_intersects
1.21% qemu-kvm [.] vring_map
0.93% qemu-kvm [.] virtio_notify
Do you have any thoughts to decrease the cpu overhead and get higher through
output? Thanks!
Regards,
-Gonglei
> Paolo
>
> > Testing AES-128-CBC cipher:
> > Encrypting in chunks of 256 bytes: done. 371.94 MiB in 5.02 secs:
> 74.12 MiB/sec (1523475 packets)
> > Encrypting in chunks of 256 bytes: done. 369.85 MiB in 5.01 secs:
> 73.88 MiB/sec (1514900 packets)
> > Encrypting in chunks of 256 bytes: done. 371.07 MiB in 5.02 secs:
> 73.97 MiB/sec (1519914 packets)
> > Encrypting in chunks of 256 bytes: done. 371.66 MiB in 5.02 secs:
> 74.09 MiB/sec (1522309 packets)
> > Encrypting in chunks of 256 bytes: done. 371.79 MiB in 5.02 secs:
> 74.12 MiB/sec (1522868 packets)
> > Encrypting in chunks of 256 bytes: done. 371.94 MiB in 5.02 secs:
> 74.15 MiB/sec (1523457 packets)
> > Encrypting in chunks of 256 bytes: done. 371.90 MiB in 5.02 secs:
> 74.14 MiB/sec (1523317 packets)
> > Encrypting in chunks of 256 bytes: done. 371.71 MiB in 5.02 secs:
> 74.10 MiB/sec (1522522 packets)
> >
> > 15.95% qemu-kvm [.] address_space_translate
> > 6.98% qemu-kvm [.] qemu_get_ram_ptr
> > 4.87% libpthread-2.19.so [.] __pthread_mutex_unlock_usercnt
> > 4.40% qemu-kvm [.] qemu_ram_addr_from_host
> > 3.79% qemu-kvm [.] address_space_map
> > 3.41% libc-2.19.so [.] _int_malloc
> > 3.29% libc-2.19.so [.] _int_free
> > 3.07% libc-2.19.so [.] malloc
> > 2.95% libpthread-2.19.so [.] pthread_mutex_lock
> > 2.94% qemu-kvm [.] phys_page_find
> > 2.73% qemu-kvm [.]
> address_space_translate_internal
> > 2.65% libc-2.19.so [.] malloc_consolidate
> > 2.35% libc-2.19.so [.] __memcpy_sse2_unaligned
> > 1.72% qemu-kvm [.] find_next_zero_bit
> > 1.38% qemu-kvm [.] address_space_rw
> > 1.34% qemu-kvm [.] object_unref
> > 1.30% qemu-kvm [.] object_ref
> > 1.28% qemu-kvm [.] virtqueue_pop
> > 1.20% libc-2.19.so [.] memset
> > 1.11% qemu-kvm [.] virtio_notify
> >
> > Thank you so much!
> >
> > Regards,
> > -Gonglei
> >
> >> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> >> index 79a635f..2433866 100644
> >> --- a/hw/virtio/virtio.c
> >> +++ b/hw/virtio/virtio.c
> >> @@ -107,35 +107,15 @@ void virtio_queue_update_rings(VirtIODevice
> *vdev,
> >> int n)
> >> vring->align);
> >> }
> >>
> >> -static inline uint64_t vring_desc_addr(VirtIODevice *vdev, hwaddr desc_pa,
> >> - int i)
> >> +static void vring_desc_read(VirtIODevice *vdev, VRingDesc *desc,
> >> + hwaddr desc_pa, int i)
> >> {
> >> - hwaddr pa;
> >> - pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, addr);
> >> - return virtio_ldq_phys(vdev, pa);
> >> -}
> >> -
> >> -static inline uint32_t vring_desc_len(VirtIODevice *vdev, hwaddr desc_pa,
> int
> >> i)
> >> -{
> >> - hwaddr pa;
> >> - pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, len);
> >> - return virtio_ldl_phys(vdev, pa);
> >> -}
> >> -
> >> -static inline uint16_t vring_desc_flags(VirtIODevice *vdev, hwaddr
> desc_pa,
> >> - int i)
> >> -{
> >> - hwaddr pa;
> >> - pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, flags);
> >> - return virtio_lduw_phys(vdev, pa);
> >> -}
> >> -
> >> -static inline uint16_t vring_desc_next(VirtIODevice *vdev, hwaddr desc_pa,
> >> - int i)
> >> -{
> >> - hwaddr pa;
> >> - pa = desc_pa + sizeof(VRingDesc) * i + offsetof(VRingDesc, next);
> >> - return virtio_lduw_phys(vdev, pa);
> >> + address_space_read(&address_space_memory, desc_pa + i *
> >> sizeof(VRingDesc),
> >> + MEMTXATTRS_UNSPECIFIED, (void *)desc,
> >> sizeof(VRingDesc));
> >> + virtio_tswap64s(vdev, &desc->addr);
> >> + virtio_tswap32s(vdev, &desc->len);
> >> + virtio_tswap16s(vdev, &desc->flags);
> >> + virtio_tswap16s(vdev, &desc->next);
> >> }
> >>
> >> static inline uint16_t vring_avail_flags(VirtQueue *vq)
> >> @@ -345,18 +325,18 @@ static unsigned int
> virtqueue_get_head(VirtQueue
> >> *vq, unsigned int idx)
> >> return head;
> >> }
> >>
> >> -static unsigned virtqueue_next_desc(VirtIODevice *vdev, hwaddr desc_pa,
> >> - unsigned int i, unsigned int
> max)
> >> +static unsigned virtqueue_read_next_desc(VirtIODevice *vdev, VRingDesc
> >> *desc,
> >> + hwaddr desc_pa,
> unsigned
> >> int max)
> >> {
> >> unsigned int next;
> >>
> >> /* If this descriptor says it doesn't chain, we're done. */
> >> - if (!(vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_NEXT)) {
> >> + if (!(desc->flags & VRING_DESC_F_NEXT)) {
> >> return max;
> >> }
> >>
> >> /* Check they're not leading us off end of descriptors. */
> >> - next = vring_desc_next(vdev, desc_pa, i);
> >> + next = desc->next;
> >> /* Make sure compiler knows to grab that: we don't want it changing!
> */
> >> smp_wmb();
> >>
> >> @@ -365,6 +345,7 @@ static unsigned virtqueue_next_desc(VirtIODevice
> >> *vdev, hwaddr desc_pa,
> >> exit(1);
> >> }
> >>
> >> + vring_desc_read(vdev, desc, desc_pa, next);
> >> return next;
> >> }
> >>
> >> @@ -381,6 +362,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq,
> >> unsigned int *in_bytes,
> >> while (virtqueue_num_heads(vq, idx)) {
> >> VirtIODevice *vdev = vq->vdev;
> >> unsigned int max, num_bufs, indirect = 0;
> >> + VRingDesc desc;
> >> hwaddr desc_pa;
> >> int i;
> >>
> >> @@ -388,9 +370,10 @@ void virtqueue_get_avail_bytes(VirtQueue *vq,
> >> unsigned int *in_bytes,
> >> num_bufs = total_bufs;
> >> i = virtqueue_get_head(vq, idx++);
> >> desc_pa = vq->vring.desc;
> >> + vring_desc_read(vdev, &desc, desc_pa, i);
> >>
> >> - if (vring_desc_flags(vdev, desc_pa, i) &
> VRING_DESC_F_INDIRECT) {
> >> - if (vring_desc_len(vdev, desc_pa, i) % sizeof(VRingDesc)) {
> >> + if (desc.flags & VRING_DESC_F_INDIRECT) {
> >> + if (desc.len % sizeof(VRingDesc)) {
> >> error_report("Invalid size for indirect buffer table");
> >> exit(1);
> >> }
> >> @@ -403,9 +386,10 @@ void virtqueue_get_avail_bytes(VirtQueue *vq,
> >> unsigned int *in_bytes,
> >>
> >> /* loop over the indirect descriptor table */
> >> indirect = 1;
> >> - max = vring_desc_len(vdev, desc_pa, i) / sizeof(VRingDesc);
> >> - desc_pa = vring_desc_addr(vdev, desc_pa, i);
> >> + max = desc.len / sizeof(VRingDesc);
> >> + desc_pa = desc.addr;
> >> num_bufs = i = 0;
> >> + vring_desc_read(vdev, &desc, desc_pa, i);
> >> }
> >>
> >> do {
> >> @@ -415,15 +399,15 @@ void virtqueue_get_avail_bytes(VirtQueue *vq,
> >> unsigned int *in_bytes,
> >> exit(1);
> >> }
> >>
> >> - if (vring_desc_flags(vdev, desc_pa, i) &
> VRING_DESC_F_WRITE)
> >> {
> >> - in_total += vring_desc_len(vdev, desc_pa, i);
> >> + if (desc.flags & VRING_DESC_F_WRITE) {
> >> + in_total += desc.len;
> >> } else {
> >> - out_total += vring_desc_len(vdev, desc_pa, i);
> >> + out_total += desc.len;
> >> }
> >> if (in_total >= max_in_bytes && out_total >=
> max_out_bytes) {
> >> goto done;
> >> }
> >> - } while ((i = virtqueue_next_desc(vdev, desc_pa, i, max)) != max);
> >> + } while ((i = virtqueue_read_next_desc(vdev, &desc, desc_pa,
> >> max)) != max);
> >>
> >> if (!indirect)
> >> total_bufs = num_bufs;
> >> @@ -545,6 +529,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
> >> unsigned out_num, in_num;
> >> hwaddr addr[VIRTQUEUE_MAX_SIZE];
> >> struct iovec iov[VIRTQUEUE_MAX_SIZE];
> >> + VRingDesc desc;
> >>
> >> if (!virtqueue_num_heads(vq, vq->last_avail_idx)) {
> >> return NULL;
> >> @@ -560,33 +545,32 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
> >> vring_set_avail_event(vq, vq->last_avail_idx);
> >> }
> >>
> >> - if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_INDIRECT) {
> >> - if (vring_desc_len(vdev, desc_pa, i) % sizeof(VRingDesc)) {
> >> + vring_desc_read(vdev, &desc, desc_pa, i);
> >> + if (desc.flags & VRING_DESC_F_INDIRECT) {
> >> + if (desc.len % sizeof(VRingDesc)) {
> >> error_report("Invalid size for indirect buffer table");
> >> exit(1);
> >> }
> >>
> >> /* loop over the indirect descriptor table */
> >> - max = vring_desc_len(vdev, desc_pa, i) / sizeof(VRingDesc);
> >> - desc_pa = vring_desc_addr(vdev, desc_pa, i);
> >> + max = desc.len / sizeof(VRingDesc);
> >> + desc_pa = desc.addr;
> >> i = 0;
> >> + vring_desc_read(vdev, &desc, desc_pa, i);
> >> }
> >>
> >> /* Collect all the descriptors */
> >> do {
> >> - hwaddr pa = vring_desc_addr(vdev, desc_pa, i);
> >> - size_t len = vring_desc_len(vdev, desc_pa, i);
> >> -
> >> - if (vring_desc_flags(vdev, desc_pa, i) & VRING_DESC_F_WRITE) {
> >> + if (desc.flags & VRING_DESC_F_WRITE) {
> >> virtqueue_map_desc(&in_num, addr + out_num, iov +
> >> out_num,
> >> - VIRTQUEUE_MAX_SIZE - out_num,
> true,
> >> pa, len);
> >> + VIRTQUEUE_MAX_SIZE - out_num,
> true,
> >> desc.addr, desc.len);
> >> } else {
> >> if (in_num) {
> >> error_report("Incorrect order for descriptors");
> >> exit(1);
> >> }
> >> virtqueue_map_desc(&out_num, addr, iov,
> >> - VIRTQUEUE_MAX_SIZE, false, pa,
> len);
> >> + VIRTQUEUE_MAX_SIZE, false,
> >> desc.addr, desc.len);
> >> }
> >>
> >> /* If we've got too many, that implies a descriptor loop. */
> >> @@ -594,7 +578,7 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
> >> error_report("Looped descriptor");
> >> exit(1);
> >> }
> >> - } while ((i = virtqueue_next_desc(vdev, desc_pa, i, max)) != max);
> >> + } while ((i = virtqueue_read_next_desc(vdev, &desc, desc_pa, max)) !=
> >> max);
> >>
> >> /* Now copy what we have collected and mapped */
> >> elem = virtqueue_alloc_element(sz, out_num, in_num);
> >> --
> >> 2.5.0
> >>
> >>
> >
> >
> >