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 at 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;
+ } 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
Michael S. Tsirkin
2021-Oct-27 08:55 UTC
[PATCH 1/3] virtio: cache indirect desc for split
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 at 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 4Add 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 at 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); >
Michael S. Tsirkin
2021-Oct-27 17:07 UTC
[PATCH 1/3] virtio: cache indirect desc for split
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 at 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? -- MST
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 at 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 at lists.01.org
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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 at 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 at lists.01.org
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