| Message ID | 20211027061913.76276-2-xuanzhuo@linux.alibaba.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | virtio support cache indirect desc | expand |
| Context | Check | Description |
|---|---|---|
| netdev/tree_selection | success | Not a local patch |
On Wed, Oct 27, 2021 at 02:19:11PM +0800, Xuan Zhuo wrote: > In the case of using indirect, indirect desc must be allocated and > released each time, which increases a lot of cpu overhead. > > Here, a cache is added for indirect. If the number of indirect desc to be > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > drivers/virtio/virtio.c | 6 ++++ > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > include/linux/virtio.h | 10 ++++++ > 3 files changed, 70 insertions(+), 9 deletions(-) > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 0a5b54034d4b..04bcb74e5b9a 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > } > EXPORT_SYMBOL_GPL(is_virtio_device); > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > +{ > + dev->desc_cache = val; > +} > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > + > void unregister_virtio_device(struct virtio_device *dev) > { > int index = dev->index; /* save for after device release */ > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index dd95dfd85e98..0b9a8544b0e8 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -117,6 +117,10 @@ struct vring_virtqueue { > /* Hint for event idx: already triggered no need to disable. */ > bool event_triggered; > > + /* Is indirect cache used? */ > + bool use_desc_cache; > + void *desc_cache_chain; > + > union { > /* Available for split ring */ > struct { Let's use llist_head and friends please (I am guessing we want single-linked to avoid writing into indirect buffer after use, invalidating the cache, but please document why in a comment). Do not open-code it. Also hide all casts in inline wrappers. > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > return extra[i].next; > } > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 Add an inline wrapper for checking sg versus VIRT_QUEUE_CACHE_DESC_NUM. > + > +static void desc_cache_chain_free_split(void *chain) > +{ > + struct vring_desc *desc; > + > + while (chain) { > + desc = chain; > + chain = (void *)desc->addr; > + kfree(desc); > + } > +} > + > +static void desc_cache_put_split(struct vring_virtqueue *vq, > + struct vring_desc *desc, int n) > +{ > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > + desc->addr = (u64)vq->desc_cache_chain; > + vq->desc_cache_chain = desc; > + } else { > + kfree(desc); > + } > +} > + > +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, > unsigned int total_sg, > gfp_t gfp) > { > struct vring_desc *desc; > - unsigned int i; > + unsigned int i, n; > + > + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { > + if (vq->desc_cache_chain) { > + desc = vq->desc_cache_chain; > + vq->desc_cache_chain = (void *)desc->addr; > + goto got; > + } > + n = VIRT_QUEUE_CACHE_DESC_NUM; Hmm. This will allocate more entries than actually used. Why do it? > + } else { > + n = total_sg; > + } > > /* > * We require lowmem mappings for the descriptors because > @@ -437,12 +476,13 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > */ > gfp &= ~__GFP_HIGHMEM; > > - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); > + desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); > if (!desc) > return NULL; > > +got: > for (i = 0; i < total_sg; i++) > - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); > + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); > return desc; > } > > @@ -508,7 +548,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > head = vq->free_head; > > if (virtqueue_use_indirect(_vq, total_sg)) > - desc = alloc_indirect_split(_vq, total_sg, gfp); > + desc = alloc_indirect_split(vq, total_sg, gfp); > else { > desc = NULL; > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > @@ -652,7 +692,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > } > > if (indirect) > - kfree(desc); > + desc_cache_put_split(vq, desc, total_sg); > > END_USE(vq); > return -ENOMEM; > @@ -717,7 +757,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > if (vq->indirect) { > struct vring_desc *indir_desc = > vq->split.desc_state[head].indir_desc; > - u32 len; > + u32 len, n; > > /* Free the indirect table, if any, now that it's unmapped. */ > if (!indir_desc) > @@ -729,10 +769,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > VRING_DESC_F_INDIRECT)); > BUG_ON(len == 0 || len % sizeof(struct vring_desc)); > > - for (j = 0; j < len / sizeof(struct vring_desc); j++) > + n = len / sizeof(struct vring_desc); > + > + for (j = 0; j < n; j++) > vring_unmap_one_split_indirect(vq, &indir_desc[j]); > > - kfree(indir_desc); > + desc_cache_put_split(vq, indir_desc, n); > vq->split.desc_state[head].indir_desc = NULL; > } else if (ctx) { > *ctx = vq->split.desc_state[head].indir_desc; > @@ -2199,6 +2241,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > !context; > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > + vq->desc_cache_chain = NULL; > + vq->use_desc_cache = vdev->desc_cache; > > if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > vq->weak_barriers = false; > @@ -2329,6 +2373,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) > if (!vq->packed_ring) { > kfree(vq->split.desc_state); > kfree(vq->split.desc_extra); > + desc_cache_chain_free_split(vq->desc_cache_chain); > } > kfree(vq); > } > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index 41edbc01ffa4..d84b7b8f4070 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -109,6 +109,7 @@ struct virtio_device { > bool failed; > bool config_enabled; > bool config_change_pending; > + bool desc_cache; > spinlock_t config_lock; > spinlock_t vqs_list_lock; /* Protects VQs list access */ > struct device dev; > @@ -130,6 +131,15 @@ int register_virtio_device(struct virtio_device *dev); > void unregister_virtio_device(struct virtio_device *dev); > bool is_virtio_device(struct device *dev); > > +/** > + * virtio_use_desc_cache - virtio ring use desc cache > + * > + * virtio will cache the allocated indirect desc. > + * > + * This function must be called before find_vqs. > + */ > +void virtio_use_desc_cache(struct virtio_device *dev, bool val); > + > void virtio_break_device(struct virtio_device *dev); > > void virtio_config_changed(struct virtio_device *dev); > -- > 2.31.0
On 10/26/21 11:19 PM, Xuan Zhuo wrote: > In the case of using indirect, indirect desc must be allocated and > released each time, which increases a lot of cpu overhead. > > Here, a cache is added for indirect. If the number of indirect desc to be > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > drivers/virtio/virtio.c | 6 ++++ > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > include/linux/virtio.h | 10 ++++++ > 3 files changed, 70 insertions(+), 9 deletions(-) > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 0a5b54034d4b..04bcb74e5b9a 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > } > EXPORT_SYMBOL_GPL(is_virtio_device); > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > +{ > + dev->desc_cache = val; > +} > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > + > void unregister_virtio_device(struct virtio_device *dev) > { > int index = dev->index; /* save for after device release */ > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index dd95dfd85e98..0b9a8544b0e8 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -117,6 +117,10 @@ struct vring_virtqueue { > /* Hint for event idx: already triggered no need to disable. */ > bool event_triggered; > > + /* Is indirect cache used? */ > + bool use_desc_cache; > + void *desc_cache_chain; > + > union { > /* Available for split ring */ > struct { > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > return extra[i].next; > } > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > + > +static void desc_cache_chain_free_split(void *chain) > +{ > + struct vring_desc *desc; > + > + while (chain) { > + desc = chain; > + chain = (void *)desc->addr; > + kfree(desc); > + } > +} > + > +static void desc_cache_put_split(struct vring_virtqueue *vq, > + struct vring_desc *desc, int n) > +{ > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > + desc->addr = (u64)vq->desc_cache_chain; > + vq->desc_cache_chain = desc; > + } else { > + kfree(desc); > + } > +} > + > +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, > unsigned int total_sg, > gfp_t gfp) > { > struct vring_desc *desc; > - unsigned int i; > + unsigned int i, n; > + > + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { > + if (vq->desc_cache_chain) { > + desc = vq->desc_cache_chain; > + vq->desc_cache_chain = (void *)desc->addr; > + goto got; > + } > + n = VIRT_QUEUE_CACHE_DESC_NUM; How about to make the VIRT_QUEUE_CACHE_DESC_NUM configurable (at least during driver probing) unless there is a reason that the default value is 4. Thank you very much! Dongli Zhang > + } else { > + n = total_sg; > + } > > /* > * We require lowmem mappings for the descriptors because > @@ -437,12 +476,13 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > */ > gfp &= ~__GFP_HIGHMEM; > > - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); > + desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); > if (!desc) > return NULL; > > +got: > for (i = 0; i < total_sg; i++) > - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); > + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); > return desc; > } > > @@ -508,7 +548,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > head = vq->free_head; > > if (virtqueue_use_indirect(_vq, total_sg)) > - desc = alloc_indirect_split(_vq, total_sg, gfp); > + desc = alloc_indirect_split(vq, total_sg, gfp); > else { > desc = NULL; > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > @@ -652,7 +692,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > } > > if (indirect) > - kfree(desc); > + desc_cache_put_split(vq, desc, total_sg); > > END_USE(vq); > return -ENOMEM; > @@ -717,7 +757,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > if (vq->indirect) { > struct vring_desc *indir_desc = > vq->split.desc_state[head].indir_desc; > - u32 len; > + u32 len, n; > > /* Free the indirect table, if any, now that it's unmapped. */ > if (!indir_desc) > @@ -729,10 +769,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > VRING_DESC_F_INDIRECT)); > BUG_ON(len == 0 || len % sizeof(struct vring_desc)); > > - for (j = 0; j < len / sizeof(struct vring_desc); j++) > + n = len / sizeof(struct vring_desc); > + > + for (j = 0; j < n; j++) > vring_unmap_one_split_indirect(vq, &indir_desc[j]); > > - kfree(indir_desc); > + desc_cache_put_split(vq, indir_desc, n); > vq->split.desc_state[head].indir_desc = NULL; > } else if (ctx) { > *ctx = vq->split.desc_state[head].indir_desc; > @@ -2199,6 +2241,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > !context; > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > + vq->desc_cache_chain = NULL; > + vq->use_desc_cache = vdev->desc_cache; > > if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > vq->weak_barriers = false; > @@ -2329,6 +2373,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) > if (!vq->packed_ring) { > kfree(vq->split.desc_state); > kfree(vq->split.desc_extra); > + desc_cache_chain_free_split(vq->desc_cache_chain); > } > kfree(vq); > } > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > index 41edbc01ffa4..d84b7b8f4070 100644 > --- a/include/linux/virtio.h > +++ b/include/linux/virtio.h > @@ -109,6 +109,7 @@ struct virtio_device { > bool failed; > bool config_enabled; > bool config_change_pending; > + bool desc_cache; > spinlock_t config_lock; > spinlock_t vqs_list_lock; /* Protects VQs list access */ > struct device dev; > @@ -130,6 +131,15 @@ int register_virtio_device(struct virtio_device *dev); > void unregister_virtio_device(struct virtio_device *dev); > bool is_virtio_device(struct device *dev); > > +/** > + * virtio_use_desc_cache - virtio ring use desc cache > + * > + * virtio will cache the allocated indirect desc. > + * > + * This function must be called before find_vqs. > + */ > +void virtio_use_desc_cache(struct virtio_device *dev, bool val); > + > void virtio_break_device(struct virtio_device *dev); > > void virtio_config_changed(struct virtio_device *dev); >
On Wed, Oct 27, 2021 at 02:19:11PM +0800, Xuan Zhuo wrote: > In the case of using indirect, indirect desc must be allocated and > released each time, which increases a lot of cpu overhead. > > Here, a cache is added for indirect. If the number of indirect desc to be > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > --- > drivers/virtio/virtio.c | 6 ++++ > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > include/linux/virtio.h | 10 ++++++ > 3 files changed, 70 insertions(+), 9 deletions(-) > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > index 0a5b54034d4b..04bcb74e5b9a 100644 > --- a/drivers/virtio/virtio.c > +++ b/drivers/virtio/virtio.c > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > } > EXPORT_SYMBOL_GPL(is_virtio_device); > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > +{ > + dev->desc_cache = val; > +} > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > + > void unregister_virtio_device(struct virtio_device *dev) > { > int index = dev->index; /* save for after device release */ > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > index dd95dfd85e98..0b9a8544b0e8 100644 > --- a/drivers/virtio/virtio_ring.c > +++ b/drivers/virtio/virtio_ring.c > @@ -117,6 +117,10 @@ struct vring_virtqueue { > /* Hint for event idx: already triggered no need to disable. */ > bool event_triggered; > > + /* Is indirect cache used? */ > + bool use_desc_cache; > + void *desc_cache_chain; > + > union { > /* Available for split ring */ > struct { > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > return extra[i].next; > } > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > + > +static void desc_cache_chain_free_split(void *chain) > +{ > + struct vring_desc *desc; > + > + while (chain) { > + desc = chain; > + chain = (void *)desc->addr; > + kfree(desc); > + } > +} > + > +static void desc_cache_put_split(struct vring_virtqueue *vq, > + struct vring_desc *desc, int n) > +{ > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > + desc->addr = (u64)vq->desc_cache_chain; > + vq->desc_cache_chain = desc; > + } else { > + kfree(desc); > + } > +} > + So I have a question here. What happens if we just do: if (n <= VIRT_QUEUE_CACHE_DESC_NUM) { return kmem_cache_alloc(VIRT_QUEUE_CACHE_DESC_NUM * sizeof desc, gfp) } else { return kmalloc_arrat(n, sizeof desc, gfp) } A small change and won't we reap most performance benefits?
On Wed, Oct 27, 2021 at 09:33:46AM -0700, Dongli Zhang wrote: > > > On 10/26/21 11:19 PM, Xuan Zhuo wrote: > > In the case of using indirect, indirect desc must be allocated and > > released each time, which increases a lot of cpu overhead. > > > > Here, a cache is added for indirect. If the number of indirect desc to be > > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > > --- > > drivers/virtio/virtio.c | 6 ++++ > > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > > include/linux/virtio.h | 10 ++++++ > > 3 files changed, 70 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > index 0a5b54034d4b..04bcb74e5b9a 100644 > > --- a/drivers/virtio/virtio.c > > +++ b/drivers/virtio/virtio.c > > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > > } > > EXPORT_SYMBOL_GPL(is_virtio_device); > > > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > > +{ > > + dev->desc_cache = val; > > +} > > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > > + > > void unregister_virtio_device(struct virtio_device *dev) > > { > > int index = dev->index; /* save for after device release */ > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index dd95dfd85e98..0b9a8544b0e8 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -117,6 +117,10 @@ struct vring_virtqueue { > > /* Hint for event idx: already triggered no need to disable. */ > > bool event_triggered; > > > > + /* Is indirect cache used? */ > > + bool use_desc_cache; > > + void *desc_cache_chain; > > + > > union { > > /* Available for split ring */ > > struct { > > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > > return extra[i].next; > > } > > > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > > + > > +static void desc_cache_chain_free_split(void *chain) > > +{ > > + struct vring_desc *desc; > > + > > + while (chain) { > > + desc = chain; > > + chain = (void *)desc->addr; > > + kfree(desc); > > + } > > +} > > + > > +static void desc_cache_put_split(struct vring_virtqueue *vq, > > + struct vring_desc *desc, int n) > > +{ > > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > > + desc->addr = (u64)vq->desc_cache_chain; > > + vq->desc_cache_chain = desc; > > + } else { > > + kfree(desc); > > + } > > +} > > + > > +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, > > unsigned int total_sg, > > gfp_t gfp) > > { > > struct vring_desc *desc; > > - unsigned int i; > > + unsigned int i, n; > > + > > + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { > > + if (vq->desc_cache_chain) { > > + desc = vq->desc_cache_chain; > > + vq->desc_cache_chain = (void *)desc->addr; > > + goto got; > > + } > > + n = VIRT_QUEUE_CACHE_DESC_NUM; > > How about to make the VIRT_QUEUE_CACHE_DESC_NUM configurable (at least during > driver probing) unless there is a reason that the default value is 4. > > Thank you very much! > > Dongli Zhang I would start with some experimentation showing that it actually makes a difference in performance. > > > > + } else { > > + n = total_sg; > > + } > > > > /* > > * We require lowmem mappings for the descriptors because > > @@ -437,12 +476,13 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > */ > > gfp &= ~__GFP_HIGHMEM; > > > > - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); > > + desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); > > if (!desc) > > return NULL; > > > > +got: > > for (i = 0; i < total_sg; i++) > > - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); > > + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); > > return desc; > > } > > > > @@ -508,7 +548,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > head = vq->free_head; > > > > if (virtqueue_use_indirect(_vq, total_sg)) > > - desc = alloc_indirect_split(_vq, total_sg, gfp); > > + desc = alloc_indirect_split(vq, total_sg, gfp); > > else { > > desc = NULL; > > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > > @@ -652,7 +692,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > } > > > > if (indirect) > > - kfree(desc); > > + desc_cache_put_split(vq, desc, total_sg); > > > > END_USE(vq); > > return -ENOMEM; > > @@ -717,7 +757,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > > if (vq->indirect) { > > struct vring_desc *indir_desc = > > vq->split.desc_state[head].indir_desc; > > - u32 len; > > + u32 len, n; > > > > /* Free the indirect table, if any, now that it's unmapped. */ > > if (!indir_desc) > > @@ -729,10 +769,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > > VRING_DESC_F_INDIRECT)); > > BUG_ON(len == 0 || len % sizeof(struct vring_desc)); > > > > - for (j = 0; j < len / sizeof(struct vring_desc); j++) > > + n = len / sizeof(struct vring_desc); > > + > > + for (j = 0; j < n; j++) > > vring_unmap_one_split_indirect(vq, &indir_desc[j]); > > > > - kfree(indir_desc); > > + desc_cache_put_split(vq, indir_desc, n); > > vq->split.desc_state[head].indir_desc = NULL; > > } else if (ctx) { > > *ctx = vq->split.desc_state[head].indir_desc; > > @@ -2199,6 +2241,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > !context; > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + vq->desc_cache_chain = NULL; > > + vq->use_desc_cache = vdev->desc_cache; > > > > if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > > vq->weak_barriers = false; > > @@ -2329,6 +2373,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) > > if (!vq->packed_ring) { > > kfree(vq->split.desc_state); > > kfree(vq->split.desc_extra); > > + desc_cache_chain_free_split(vq->desc_cache_chain); > > } > > kfree(vq); > > } > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > index 41edbc01ffa4..d84b7b8f4070 100644 > > --- a/include/linux/virtio.h > > +++ b/include/linux/virtio.h > > @@ -109,6 +109,7 @@ struct virtio_device { > > bool failed; > > bool config_enabled; > > bool config_change_pending; > > + bool desc_cache; > > spinlock_t config_lock; > > spinlock_t vqs_list_lock; /* Protects VQs list access */ > > struct device dev; > > @@ -130,6 +131,15 @@ int register_virtio_device(struct virtio_device *dev); > > void unregister_virtio_device(struct virtio_device *dev); > > bool is_virtio_device(struct device *dev); > > > > +/** > > + * virtio_use_desc_cache - virtio ring use desc cache > > + * > > + * virtio will cache the allocated indirect desc. > > + * > > + * This function must be called before find_vqs. > > + */ > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val); > > + > > void virtio_break_device(struct virtio_device *dev); > > > > void virtio_config_changed(struct virtio_device *dev); > >
Hi Xuan,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on horms-ipvs/master]
[also build test WARNING on linus/master v5.15-rc7 next-20211027]
[cannot apply to mst-vhost/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Xuan-Zhuo/virtio-support-cache-indirect-desc/20211027-142025
base: https://git.kernel.org/pub/scm/linux/kernel/git/horms/ipvs.git master
config: arm-defconfig (attached as .config)
compiler: arm-linux-gnueabi-gcc (GCC) 11.2.0
reproduce (this is a W=1 build):
wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
chmod +x ~/bin/make.cross
# https://github.com/0day-ci/linux/commit/8935e116c155fb7d484bad35a42b2ca98f75e384
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Xuan-Zhuo/virtio-support-cache-indirect-desc/20211027-142025
git checkout 8935e116c155fb7d484bad35a42b2ca98f75e384
# save the attached .config to linux build tree
COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-11.2.0 make.cross ARCH=arm
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
All warnings (new ones prefixed by >>):
drivers/virtio/virtio_ring.c: In function 'desc_cache_chain_free_split':
>> drivers/virtio/virtio_ring.c:438:25: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
438 | chain = (void *)desc->addr;
| ^
drivers/virtio/virtio_ring.c: In function 'desc_cache_put_split':
>> drivers/virtio/virtio_ring.c:447:30: warning: cast from pointer to integer of different size [-Wpointer-to-int-cast]
447 | desc->addr = (u64)vq->desc_cache_chain;
| ^
drivers/virtio/virtio_ring.c: In function 'alloc_indirect_split':
drivers/virtio/virtio_ring.c:464:48: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]
464 | vq->desc_cache_chain = (void *)desc->addr;
| ^
vim +438 drivers/virtio/virtio_ring.c
431
432 static void desc_cache_chain_free_split(void *chain)
433 {
434 struct vring_desc *desc;
435
436 while (chain) {
437 desc = chain;
> 438 chain = (void *)desc->addr;
439 kfree(desc);
440 }
441 }
442
443 static void desc_cache_put_split(struct vring_virtqueue *vq,
444 struct vring_desc *desc, int n)
445 {
446 if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) {
> 447 desc->addr = (u64)vq->desc_cache_chain;
448 vq->desc_cache_chain = desc;
449 } else {
450 kfree(desc);
451 }
452 }
453
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
Hi Xuan,
Thank you for the patch! Perhaps something to improve:
[auto build test WARNING on horms-ipvs/master]
[also build test WARNING on linus/master v5.15-rc7 next-20211027]
[cannot apply to mst-vhost/linux-next]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch]
url: https://github.com/0day-ci/linux/commits/Xuan-Zhuo/virtio-support-cache-indirect-desc/20211027-142025
base: https://git.kernel.org/pub/scm/linux/kernel/git/horms/ipvs.git master
config: i386-randconfig-s002-20211027 (attached as .config)
compiler: gcc-9 (Debian 9.3.0-22) 9.3.0
reproduce:
# apt-get install sparse
# sparse version: v0.6.4-dirty
# https://github.com/0day-ci/linux/commit/8935e116c155fb7d484bad35a42b2ca98f75e384
git remote add linux-review https://github.com/0day-ci/linux
git fetch --no-tags linux-review Xuan-Zhuo/virtio-support-cache-indirect-desc/20211027-142025
git checkout 8935e116c155fb7d484bad35a42b2ca98f75e384
# save the attached .config to linux build tree
make W=1 C=1 CF='-fdiagnostic-prefix -D__CHECK_ENDIAN__' O=build_dir ARCH=i386 SHELL=/bin/bash drivers/virtio/
If you fix the issue, kindly add following tag as appropriate
Reported-by: kernel test robot <lkp@intel.com>
sparse warnings: (new ones prefixed by >>)
>> drivers/virtio/virtio_ring.c:438:26: sparse: sparse: cast from restricted __virtio64
>> drivers/virtio/virtio_ring.c:447:28: sparse: sparse: incorrect type in assignment (different base types) @@ expected restricted __virtio64 [usertype] addr @@ got unsigned long long [usertype] @@
drivers/virtio/virtio_ring.c:447:28: sparse: expected restricted __virtio64 [usertype] addr
drivers/virtio/virtio_ring.c:447:28: sparse: got unsigned long long [usertype]
drivers/virtio/virtio_ring.c:464:49: sparse: sparse: cast from restricted __virtio64
vim +438 drivers/virtio/virtio_ring.c
431
432 static void desc_cache_chain_free_split(void *chain)
433 {
434 struct vring_desc *desc;
435
436 while (chain) {
437 desc = chain;
> 438 chain = (void *)desc->addr;
439 kfree(desc);
440 }
441 }
442
443 static void desc_cache_put_split(struct vring_virtqueue *vq,
444 struct vring_desc *desc, int n)
445 {
446 if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) {
> 447 desc->addr = (u64)vq->desc_cache_chain;
448 vq->desc_cache_chain = desc;
449 } else {
450 kfree(desc);
451 }
452 }
453
---
0-DAY CI Kernel Test Service, Intel Corporation
https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org
On Thu, Oct 28, 2021 at 1:07 AM Michael S. Tsirkin <mst@redhat.com> wrote: > > On Wed, Oct 27, 2021 at 02:19:11PM +0800, Xuan Zhuo wrote: > > In the case of using indirect, indirect desc must be allocated and > > released each time, which increases a lot of cpu overhead. > > > > Here, a cache is added for indirect. If the number of indirect desc to be > > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > > --- > > drivers/virtio/virtio.c | 6 ++++ > > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > > include/linux/virtio.h | 10 ++++++ > > 3 files changed, 70 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > index 0a5b54034d4b..04bcb74e5b9a 100644 > > --- a/drivers/virtio/virtio.c > > +++ b/drivers/virtio/virtio.c > > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > > } > > EXPORT_SYMBOL_GPL(is_virtio_device); > > > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > > +{ > > + dev->desc_cache = val; > > +} > > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > > + > > void unregister_virtio_device(struct virtio_device *dev) > > { > > int index = dev->index; /* save for after device release */ > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index dd95dfd85e98..0b9a8544b0e8 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -117,6 +117,10 @@ struct vring_virtqueue { > > /* Hint for event idx: already triggered no need to disable. */ > > bool event_triggered; > > > > + /* Is indirect cache used? */ > > + bool use_desc_cache; > > + void *desc_cache_chain; > > + > > union { > > /* Available for split ring */ > > struct { > > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > > return extra[i].next; > > } > > > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > > + > > +static void desc_cache_chain_free_split(void *chain) > > +{ > > + struct vring_desc *desc; > > + > > + while (chain) { > > + desc = chain; > > + chain = (void *)desc->addr; > > + kfree(desc); > > + } > > +} > > + > > +static void desc_cache_put_split(struct vring_virtqueue *vq, > > + struct vring_desc *desc, int n) > > +{ > > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > > + desc->addr = (u64)vq->desc_cache_chain; > > + vq->desc_cache_chain = desc; > > + } else { > > + kfree(desc); > > + } > > +} > > + > > > So I have a question here. What happens if we just do: > > if (n <= VIRT_QUEUE_CACHE_DESC_NUM) { > return kmem_cache_alloc(VIRT_QUEUE_CACHE_DESC_NUM * sizeof desc, gfp) > } else { > return kmalloc_arrat(n, sizeof desc, gfp) > } > > A small change and won't we reap most performance benefits? Yes, I think we need a benchmark to use private cache to see how much it can help. Thanks > > -- > MST >
On Thu, Oct 28, 2021 at 02:16:03PM +0800, Xuan Zhuo wrote: > On Thu, 28 Oct 2021 10:16:10 +0800, Jason Wang <jasowang@redhat.com> wrote: > > On Thu, Oct 28, 2021 at 1:07 AM Michael S. Tsirkin <mst@redhat.com> wrote: > > > > > > On Wed, Oct 27, 2021 at 02:19:11PM +0800, Xuan Zhuo wrote: > > > > In the case of using indirect, indirect desc must be allocated and > > > > released each time, which increases a lot of cpu overhead. > > > > > > > > Here, a cache is added for indirect. If the number of indirect desc to be > > > > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > > > > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > > > > > > > Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> > > > > --- > > > > drivers/virtio/virtio.c | 6 ++++ > > > > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > > > > include/linux/virtio.h | 10 ++++++ > > > > 3 files changed, 70 insertions(+), 9 deletions(-) > > > > > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > > > index 0a5b54034d4b..04bcb74e5b9a 100644 > > > > --- a/drivers/virtio/virtio.c > > > > +++ b/drivers/virtio/virtio.c > > > > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > > > > } > > > > EXPORT_SYMBOL_GPL(is_virtio_device); > > > > > > > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > > > > +{ > > > > + dev->desc_cache = val; > > > > +} > > > > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > > > > + > > > > void unregister_virtio_device(struct virtio_device *dev) > > > > { > > > > int index = dev->index; /* save for after device release */ > > > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > > > index dd95dfd85e98..0b9a8544b0e8 100644 > > > > --- a/drivers/virtio/virtio_ring.c > > > > +++ b/drivers/virtio/virtio_ring.c > > > > @@ -117,6 +117,10 @@ struct vring_virtqueue { > > > > /* Hint for event idx: already triggered no need to disable. */ > > > > bool event_triggered; > > > > > > > > + /* Is indirect cache used? */ > > > > + bool use_desc_cache; > > > > + void *desc_cache_chain; > > > > + > > > > union { > > > > /* Available for split ring */ > > > > struct { > > > > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > > > > return extra[i].next; > > > > } > > > > > > > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > > > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > > > > + > > > > +static void desc_cache_chain_free_split(void *chain) > > > > +{ > > > > + struct vring_desc *desc; > > > > + > > > > + while (chain) { > > > > + desc = chain; > > > > + chain = (void *)desc->addr; > > > > + kfree(desc); > > > > + } > > > > +} > > > > + > > > > +static void desc_cache_put_split(struct vring_virtqueue *vq, > > > > + struct vring_desc *desc, int n) > > > > +{ > > > > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > > > > + desc->addr = (u64)vq->desc_cache_chain; > > > > + vq->desc_cache_chain = desc; > > > > + } else { > > > > + kfree(desc); > > > > + } > > > > +} > > > > + > > > > > > > > > So I have a question here. What happens if we just do: > > > > > > if (n <= VIRT_QUEUE_CACHE_DESC_NUM) { > > > return kmem_cache_alloc(VIRT_QUEUE_CACHE_DESC_NUM * sizeof desc, gfp) > > > } else { > > > return kmalloc_arrat(n, sizeof desc, gfp) > > > } > > > > > > A small change and won't we reap most performance benefits? > > > > Yes, I think we need a benchmark to use private cache to see how much > > it can help. > > I did a test, the code is as follows: > > +static void desc_cache_put_packed(struct vring_virtqueue *vq, > + struct vring_packed_desc *desc, int n) > + { > + if (n <= VIRT_QUEUE_CACHE_DESC_NUM) { > + kmem_cache_free(vq->desc_cache, desc); > + } else { > + kfree(desc); > + } > > > @@ -476,11 +452,14 @@ static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, > */ > gfp &= ~__GFP_HIGHMEM; > > - desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); > + if (total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) > + desc = kmem_cache_alloc(vq->desc_cache, gfp); > + else > + desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); > + > > ....... > > + vq->desc_cache = kmem_cache_create("virio_desc", > + 4 * sizeof(struct vring_desc), > + 0, 0, NULL); > > The effect is not good, basically there is no improvement, using perf top can > see that the overhead of kmem_cache_alloc/kmem_cache_free is also relatively > large: > > 26.91% [kernel] [k] virtqueue_add > 15.35% [kernel] [k] detach_buf_split > 14.15% [kernel] [k] virtnet_xsk_xmit > 13.24% [kernel] [k] virtqueue_add_outbuf > > 9.30% [kernel] [k] __slab_free > > 3.91% [kernel] [k] kmem_cache_alloc > 2.85% [kernel] [k] virtqueue_get_buf_ctx > > 2.82% [kernel] [k] kmem_cache_free > 2.54% [kernel] [k] memset_erms > 2.37% [kernel] [k] xsk_tx_peek_desc > 1.20% [kernel] [k] virtnet_xsk_run > 0.81% [kernel] [k] vring_map_one_sg > 0.69% [kernel] [k] __free_old_xmit_ptr > 0.69% [kernel] [k] virtqueue_kick_prepare > 0.43% [kernel] [k] sg_init_table > 0.41% [kernel] [k] sg_next > 0.28% [kernel] [k] vring_unmap_one_split > 0.25% [kernel] [k] vring_map_single.constprop.34 > 0.24% [kernel] [k] net_rx_action > > Thanks. How about batching these? E.g. kmem_cache_alloc_bulk/kmem_cache_free_bulk? > > > > Thanks > > > > > > > > -- > > > MST > > > > >
diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c index 0a5b54034d4b..04bcb74e5b9a 100644 --- a/drivers/virtio/virtio.c +++ b/drivers/virtio/virtio.c @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) } EXPORT_SYMBOL_GPL(is_virtio_device); +void virtio_use_desc_cache(struct virtio_device *dev, bool val) +{ + dev->desc_cache = val; +} +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); + void unregister_virtio_device(struct virtio_device *dev) { int index = dev->index; /* save for after device release */ diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c index dd95dfd85e98..0b9a8544b0e8 100644 --- a/drivers/virtio/virtio_ring.c +++ b/drivers/virtio/virtio_ring.c @@ -117,6 +117,10 @@ struct vring_virtqueue { /* Hint for event idx: already triggered no need to disable. */ bool event_triggered; + /* Is indirect cache used? */ + bool use_desc_cache; + void *desc_cache_chain; + union { /* Available for split ring */ struct { @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, return extra[i].next; } -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, +#define VIRT_QUEUE_CACHE_DESC_NUM 4 + +static void desc_cache_chain_free_split(void *chain) +{ + struct vring_desc *desc; + + while (chain) { + desc = chain; + chain = (void *)desc->addr; + kfree(desc); + } +} + +static void desc_cache_put_split(struct vring_virtqueue *vq, + struct vring_desc *desc, int n) +{ + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { + desc->addr = (u64)vq->desc_cache_chain; + vq->desc_cache_chain = desc; + } else { + kfree(desc); + } +} + +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, unsigned int total_sg, gfp_t gfp) { struct vring_desc *desc; - unsigned int i; + unsigned int i, n; + + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { + if (vq->desc_cache_chain) { + desc = vq->desc_cache_chain; + vq->desc_cache_chain = (void *)desc->addr; + goto got; + } + n = VIRT_QUEUE_CACHE_DESC_NUM; + } else { + n = total_sg; + } /* * We require lowmem mappings for the descriptors because @@ -437,12 +476,13 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, */ gfp &= ~__GFP_HIGHMEM; - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); + desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); if (!desc) return NULL; +got: for (i = 0; i < total_sg; i++) - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); return desc; } @@ -508,7 +548,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, head = vq->free_head; if (virtqueue_use_indirect(_vq, total_sg)) - desc = alloc_indirect_split(_vq, total_sg, gfp); + desc = alloc_indirect_split(vq, total_sg, gfp); else { desc = NULL; WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); @@ -652,7 +692,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, } if (indirect) - kfree(desc); + desc_cache_put_split(vq, desc, total_sg); END_USE(vq); return -ENOMEM; @@ -717,7 +757,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, if (vq->indirect) { struct vring_desc *indir_desc = vq->split.desc_state[head].indir_desc; - u32 len; + u32 len, n; /* Free the indirect table, if any, now that it's unmapped. */ if (!indir_desc) @@ -729,10 +769,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, VRING_DESC_F_INDIRECT)); BUG_ON(len == 0 || len % sizeof(struct vring_desc)); - for (j = 0; j < len / sizeof(struct vring_desc); j++) + n = len / sizeof(struct vring_desc); + + for (j = 0; j < n; j++) vring_unmap_one_split_indirect(vq, &indir_desc[j]); - kfree(indir_desc); + desc_cache_put_split(vq, indir_desc, n); vq->split.desc_state[head].indir_desc = NULL; } else if (ctx) { *ctx = vq->split.desc_state[head].indir_desc; @@ -2199,6 +2241,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && !context; vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); + vq->desc_cache_chain = NULL; + vq->use_desc_cache = vdev->desc_cache; if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) vq->weak_barriers = false; @@ -2329,6 +2373,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) if (!vq->packed_ring) { kfree(vq->split.desc_state); kfree(vq->split.desc_extra); + desc_cache_chain_free_split(vq->desc_cache_chain); } kfree(vq); } diff --git a/include/linux/virtio.h b/include/linux/virtio.h index 41edbc01ffa4..d84b7b8f4070 100644 --- a/include/linux/virtio.h +++ b/include/linux/virtio.h @@ -109,6 +109,7 @@ struct virtio_device { bool failed; bool config_enabled; bool config_change_pending; + bool desc_cache; spinlock_t config_lock; spinlock_t vqs_list_lock; /* Protects VQs list access */ struct device dev; @@ -130,6 +131,15 @@ int register_virtio_device(struct virtio_device *dev); void unregister_virtio_device(struct virtio_device *dev); bool is_virtio_device(struct device *dev); +/** + * virtio_use_desc_cache - virtio ring use desc cache + * + * virtio will cache the allocated indirect desc. + * + * This function must be called before find_vqs. + */ +void virtio_use_desc_cache(struct virtio_device *dev, bool val); + void virtio_break_device(struct virtio_device *dev); void virtio_config_changed(struct virtio_device *dev);
In the case of using indirect, indirect desc must be allocated and released each time, which increases a lot of cpu overhead. Here, a cache is added for indirect. If the number of indirect desc to be applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. Signed-off-by: Xuan Zhuo <xuanzhuo@linux.alibaba.com> --- drivers/virtio/virtio.c | 6 ++++ drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ include/linux/virtio.h | 10 ++++++ 3 files changed, 70 insertions(+), 9 deletions(-)