On Fri, Apr 10, 2015 at 05:33:35PM +0800, Jason Wang wrote:
> Currently we allocate one vhost log per vhost device. This is sub
> optimal when:
>
> - Guest has several device with vhost as backend
> - Guest has multiqueue devices
>
> In the above cases, we can avoid the memory allocation by sharing a
> single vhost log among all the vhost devices. This is done through:
>
> - Introducing a new vhost_log structure with refcnt inside.
> - Using a global pointer to vhost_log structure that will be used. And
> introduce helper to get the log with expected log size and helper to
> - drop the refcnt to the old log.
> - Each vhost device still keep track of a pointer to the log that was
> used.
>
> With above, if no resize happens, all vhost device will share a single
> vhost log. During resize, a new vhost_log structure will be allocated
> and made for the global pointer. And each vhost devices will drop the
> refcnt to the old log.
>
> Tested by doing scp during migration for a 2 queues virtio-net-pci.
>
> Cc: Michael S. Tsirkin <m...@redhat.com>
> Signed-off-by: Jason Wang <jasow...@redhat.com>
> ---
> Changes from V1:
> - Drop the list of vhost log, instead, using a global pointer instead
I don't think it works like this. If you have a global pointer,
you also need a global listener, have that sync all devices.
> ---
> hw/virtio/vhost.c | 66
> ++++++++++++++++++++++++++++++++++++++---------
> include/hw/virtio/vhost.h | 9 ++++++-
> 2 files changed, 62 insertions(+), 13 deletions(-)
>
> diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
> index 5a12861..e16c2db 100644
> --- a/hw/virtio/vhost.c
> +++ b/hw/virtio/vhost.c
> @@ -22,15 +22,19 @@
> #include "hw/virtio/virtio-bus.h"
> #include "migration/migration.h"
>
> +static struct vhost_log *vhost_log;
> +
> static void vhost_dev_sync_region(struct vhost_dev *dev,
> MemoryRegionSection *section,
> uint64_t mfirst, uint64_t mlast,
> uint64_t rfirst, uint64_t rlast)
> {
> + vhost_log_chunk_t *log = dev->log->log;
> +
> uint64_t start = MAX(mfirst, rfirst);
> uint64_t end = MIN(mlast, rlast);
> - vhost_log_chunk_t *from = dev->log + start / VHOST_LOG_CHUNK;
> - vhost_log_chunk_t *to = dev->log + end / VHOST_LOG_CHUNK + 1;
> + vhost_log_chunk_t *from = log + start / VHOST_LOG_CHUNK;
> + vhost_log_chunk_t *to = log + end / VHOST_LOG_CHUNK + 1;
> uint64_t addr = (start / VHOST_LOG_CHUNK) * VHOST_LOG_CHUNK;
>
> if (end < start) {
> @@ -280,22 +284,55 @@ static uint64_t vhost_get_log_size(struct vhost_dev
> *dev)
> }
> return log_size;
> }
> +static struct vhost_log *vhost_log_alloc(uint64_t size)
> +{
> + struct vhost_log *log = g_malloc0(sizeof *log + size *
> sizeof(*(log->log)));
> +
> + log->size = size;
> + log->refcnt = 1;
> +
> + return log;
> +}
> +
> +static struct vhost_log *vhost_log_get(uint64_t size)
> +{
> + if (!vhost_log || vhost_log->size != size) {
> + vhost_log = vhost_log_alloc(size);
This just leaks the old log if size != size.
> + } else {
> + ++vhost_log->refcnt;
> + }
> +
> + return vhost_log;
> +}
> +
> +static void vhost_log_put(struct vhost_log *log)
> +{
> + if (!log) {
> + return;
> + }
> +
> + --log->refcnt;
> + if (log->refcnt == 0) {
> + if (vhost_log == log) {
> + vhost_log = NULL;
> + }
> + g_free(log);
> + }
> +}
>
> static inline void vhost_dev_log_resize(struct vhost_dev* dev, uint64_t size)
> {
> - vhost_log_chunk_t *log;
> - uint64_t log_base;
> + struct vhost_log *log = vhost_log_get(size);
At this point next device will try to use the
new log, but there is nothing there.
> + uint64_t log_base = (uint64_t)(unsigned long)log->log;
> int r;
>
> - log = g_malloc0(size * sizeof *log);
> - log_base = (uint64_t)(unsigned long)log;
> r = dev->vhost_ops->vhost_call(dev, VHOST_SET_LOG_BASE, &log_base);
> assert(r >= 0);
> /* Sync only the range covered by the old log */
> if (dev->log_size) {
> vhost_log_sync_range(dev, 0, dev->log_size * VHOST_LOG_CHUNK - 1);
> }
> - g_free(dev->log);
> + vhost_log_put(dev->log);
> dev->log = log;
> dev->log_size = size;
> }
> @@ -601,7 +638,7 @@ static int vhost_migration_log(MemoryListener *listener,
> int enable)
> if (r < 0) {
> return r;
> }
> - g_free(dev->log);
> + vhost_log_put(dev->log);
> dev->log = NULL;
> dev->log_size = 0;
> } else {
> @@ -1058,9 +1095,11 @@ int vhost_dev_start(struct vhost_dev *hdev,
> VirtIODevice *vdev)
>
> if (hdev->log_enabled) {
> hdev->log_size = vhost_get_log_size(hdev);
> - hdev->log = hdev->log_size ?
> - g_malloc0(hdev->log_size * sizeof *hdev->log) : NULL;
> - r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_LOG_BASE, hdev->log);
> + if (hdev->log_size) {
> + hdev->log = vhost_log_get(hdev->log_size);
> + }
> + r = hdev->vhost_ops->vhost_call(hdev, VHOST_SET_LOG_BASE,
> + hdev->log_size ? hdev->log->log :
> NULL);
> if (r < 0) {
> r = -errno;
> goto fail_log;
> @@ -1069,6 +1108,9 @@ int vhost_dev_start(struct vhost_dev *hdev,
> VirtIODevice *vdev)
>
> return 0;
> fail_log:
> + if (hdev->log_size) {
> + vhost_log_put(hdev->log);
> + }
> fail_vq:
> while (--i >= 0) {
> vhost_virtqueue_stop(hdev,
> @@ -1098,7 +1140,7 @@ void vhost_dev_stop(struct vhost_dev *hdev,
> VirtIODevice *vdev)
> vhost_log_sync_range(hdev, 0, ~0x0ull);
>
> hdev->started = false;
> - g_free(hdev->log);
> + vhost_log_put(hdev->log);
> hdev->log = NULL;
> hdev->log_size = 0;
> }
> diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> index d5593d1..3879778 100644
> --- a/include/hw/virtio/vhost.h
> +++ b/include/hw/virtio/vhost.h
> @@ -28,6 +28,13 @@ typedef unsigned long vhost_log_chunk_t;
> #define VHOST_LOG_CHUNK (VHOST_LOG_PAGE * VHOST_LOG_BITS)
> #define VHOST_INVALID_FEATURE_BIT (0xff)
>
> +struct vhost_log {
> + QLIST_ENTRY(vhost_log) node;
> + unsigned long long size;
> + int refcnt;
> + vhost_log_chunk_t log[0];
> +};
> +
Pls fix coding style here: typedef ... VhostLog.
> struct vhost_memory;
> struct vhost_dev {
> MemoryListener memory_listener;
> @@ -43,7 +50,6 @@ struct vhost_dev {
> unsigned long long backend_features;
> bool started;
> bool log_enabled;
> - vhost_log_chunk_t *log;
> unsigned long long log_size;
> Error *migration_blocker;
> bool force;
> @@ -52,6 +58,7 @@ struct vhost_dev {
> hwaddr mem_changed_end_addr;
> const VhostOps *vhost_ops;
> void *opaque;
> + struct vhost_log *log;
> };
>
> int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> --
> 2.1.0
