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Varka Bhadram

2014-Jul-16 08:38 UTC

[PATCH net-next V2 3/3] virtio-net: rx busy polling support

On 07/16/2014 11:51 AM, Jason Wang wrote:> Add basic support for rx busy polling.
>
> Test was done between a kvm guest and an external host. Two hosts were
> connected through 40gb mlx4 cards. With both busy_poll and busy_read
> are set to 50 in guest, 1 byte netperf tcp_rr shows 116% improvement:
> transaction rate was increased from 9151.94 to 19787.37.
>
> Cc: Rusty Russell <rusty at rustcorp.com.au>
> Cc: Michael S. Tsirkin <mst at redhat.com>
> Cc: Vlad Yasevich <vyasevic at redhat.com>
> Cc: Eric Dumazet <eric.dumazet at gmail.com>
> Signed-off-by: Jason Wang <jasowang at redhat.com>
> ---
>   drivers/net/virtio_net.c | 190
++++++++++++++++++++++++++++++++++++++++++++++-
>   1 file changed, 187 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
> index e417d93..4830713 100644
> --- a/drivers/net/virtio_net.c
> +++ b/drivers/net/virtio_net.c
> @@ -27,6 +27,7 @@
>   #include <linux/slab.h>
>   #include <linux/cpu.h>
>   #include <linux/average.h>
> +#include <net/busy_poll.h>
>   
>   static int napi_weight = NAPI_POLL_WEIGHT;
>   module_param(napi_weight, int, 0444);
> @@ -94,8 +95,143 @@ struct receive_queue {
>   
>   	/* Name of this receive queue: input.$index */
>   	char name[40];
> +
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +	unsigned int state;
> +#define VIRTNET_RQ_STATE_IDLE        0
> +#define VIRTNET_RQ_STATE_NAPI	     1    /* NAPI or refill owns this RQ */
> +#define VIRTNET_RQ_STATE_POLL	     2    /* poll owns this RQ */
> +#define VIRTNET_RQ_STATE_DISABLED    4    /* RQ is disabled */
> +#define VIRTNET_RQ_OWNED (VIRTNET_RQ_STATE_NAPI | VIRTNET_RQ_STATE_POLL)
> +#define VIRTNET_RQ_LOCKED (VIRTNET_RQ_OWNED | VIRTNET_RQ_STATE_DISABLED)
> +#define VIRTNET_RQ_STATE_NAPI_YIELD  8    /* NAPI or refill yielded this
RQ */
> +#define VIRTNET_RQ_STATE_POLL_YIELD  16   /* poll yielded this RQ */
> +	spinlock_t lock;
> +#endif  /* CONFIG_NET_RX_BUSY_POLL */
>   };
>   
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +static inline void virtnet_rq_init_lock(struct receive_queue *rq)
> +{
> +
> +	spin_lock_init(&rq->lock);
> +	rq->state = VIRTNET_RQ_STATE_IDLE;
> +}
> +
> +/* called from the device poll routine or refill routine to get ownership
of a
> + * receive queue.
> + */
> +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue *rq)
> +{
> +	int rc = true;
> +
bool instead of int...?
> +	spin_lock(&rq->lock);
> +	if (rq->state & VIRTNET_RQ_LOCKED) {
> +		WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
> +		rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
> +		rc = false;
> +	} else
> +		/* we don't care if someone yielded */
> +		rq->state = VIRTNET_RQ_STATE_NAPI;
> +	spin_unlock(&rq->lock);
Lock for rq->state ...?

If yes:
spin_lock(&rq->lock);
if (rq->state & VIRTNET_RQ_LOCKED) {
	rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
	spin_unlock(&rq->lock);
	WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
	rc = false;
} else {
	/* we don't care if someone yielded */
	rq->state = VIRTNET_RQ_STATE_NAPI;
	spin_unlock(&rq->lock);
}
> +	return rc;
> +}
> +
> +/* returns true is someone tried to get the rq while napi or refill had it
*/
> +static inline bool virtnet_rq_unlock_napi_refill(struct receive_queue *rq)
> +{
> +	int rc = false;
> +
> +	spin_lock(&rq->lock);
> +	WARN_ON(rq->state & (VIRTNET_RQ_STATE_POLL |
> +			     VIRTNET_RQ_STATE_NAPI_YIELD));
> +
> +	if (rq->state & VIRTNET_RQ_STATE_POLL_YIELD)
> +		rc = true;
> +	/* will reset state to idle, unless RQ is disabled */
> +	rq->state &= VIRTNET_RQ_STATE_DISABLED;
> +	spin_unlock(&rq->lock);
> +	return rc;
> +}
> +
> +/* called from virtnet_low_latency_recv() */
> +static inline bool virtnet_rq_lock_poll(struct receive_queue *rq)
> +{
> +	int rc = true;
> +
> +	spin_lock_bh(&rq->lock);
> +	if ((rq->state & VIRTNET_RQ_LOCKED)) {
> +		rq->state |= VIRTNET_RQ_STATE_POLL_YIELD;
> +		rc = false;
> +	} else
> +		/* preserve yield marks */
> +		rq->state |= VIRTNET_RQ_STATE_POLL;
> +	spin_unlock_bh(&rq->lock);
> +	return rc;
> +}
> +
> +/* returns true if someone tried to get the receive queue while it was
locked */
> +static inline bool virtnet_rq_unlock_poll(struct receive_queue *rq)
> +{
> +	int rc = false;
> +
> +	spin_lock_bh(&rq->lock);
> +	WARN_ON(rq->state & (VIRTNET_RQ_STATE_NAPI));
> +
> +	if (rq->state & VIRTNET_RQ_STATE_POLL_YIELD)
> +		rc = true;
> +	/* will reset state to idle, unless RQ is disabled */
> +	rq->state &= VIRTNET_RQ_STATE_DISABLED;
> +	spin_unlock_bh(&rq->lock);
> +	return rc;
> +}
> +
> +/* return false if RQ is currently owned */
> +static inline bool virtnet_rq_disable(struct receive_queue *rq)
> +{
> +	int rc = true;
> +
> +	spin_lock_bh(&rq->lock);
> +	if (rq->state & VIRTNET_RQ_OWNED)
> +		rc = false;
> +	rq->state |= VIRTNET_RQ_STATE_DISABLED;
> +	spin_unlock_bh(&rq->lock);
> +
> +	return rc;
> +}
> +
> +#else /* CONFIG_NET_RX_BUSY_POLL */
> +static inline void virtnet_rq_init_lock(struct receive_queue *rq)
> +{
> +}
> +
> +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue *rq)
> +{
> +	return true;
> +}
> +
> +static inline bool virtnet_rq_unlock_napi_refill(struct receive_queue *rq)
> +{
> +	return false;
> +}
> +
> +static inline bool virtnet_rq_lock_poll(struct receive_queue *rq)
> +{
> +	return false;
> +}
> +
> +static inline bool virtnet_rq_unlock_poll(struct receive_queue *rq)
> +{
> +	return false;
> +}
> +
> +static inline bool virtnet_rq_disable(struct receive_queue *rq)
> +{
> +	return true;
> +}
> +
> +#endif /* CONFIG_NET_RX_BUSY_POLL */
> +
>   struct virtnet_info {
>   	struct virtio_device *vdev;
>   	struct virtqueue *cvq;
> @@ -521,6 +657,8 @@ static void receive_buf(struct receive_queue *rq, void
*buf, unsigned int len)
>   		skb_shinfo(skb)->gso_segs = 0;
>   	}
>   
> +	skb_mark_napi_id(skb, &rq->napi);
> +
>   	netif_receive_skb(skb);
>   	return;
>   
> @@ -714,7 +852,12 @@ static void refill_work(struct work_struct *work)
>   		struct receive_queue *rq = &vi->rq[i];
>   
>   		napi_disable(&rq->napi);
> +		if (!virtnet_rq_lock_napi_refill(rq)) {
> +			virtnet_napi_enable(rq);
> +			continue;
> +		}
>   		still_empty = !try_fill_recv(rq, GFP_KERNEL);
> +		virtnet_rq_unlock_napi_refill(rq);
>   		virtnet_napi_enable(rq);
>   
>   		/* In theory, this can happen: if we don't get any buffers in
> @@ -752,8 +895,13 @@ static int virtnet_poll(struct napi_struct *napi, int
budget)
>   	unsigned int r, received = 0;
>   
>   again:
> +	if (!virtnet_rq_lock_napi_refill(rq))
> +		return budget;
> +
>   	received += virtnet_receive(rq, budget);
>   
> +	virtnet_rq_unlock_napi_refill(rq);
> +
>   	/* Out of packets? */
>   	if (received < budget) {
>   		r = virtqueue_enable_cb_prepare(rq->vq);
> @@ -770,20 +918,50 @@ again:
>   	return received;
>   }
>   
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +/* must be called with local_bh_disable()d */
> +static int virtnet_low_latency_recv(struct napi_struct *napi)
> +{
> +	struct receive_queue *rq > +		container_of(napi, struct receive_queue,
napi);
> +	struct virtnet_info *vi = rq->vq->vdev->priv;
> +	int received;
> +
> +	if (!(vi->status & VIRTIO_NET_S_LINK_UP))
> +		return LL_FLUSH_FAILED;
> +
> +	if (!virtnet_rq_lock_poll(rq))
> +		return LL_FLUSH_BUSY;
> +
> +	received = virtnet_receive(rq, 4);
> +
> +	virtnet_rq_unlock_poll(rq);
> +
> +	return received;
> +}
> +#endif	/* CONFIG_NET_RX_BUSY_POLL */
> +
>   static void virtnet_napi_enable_all(struct virtnet_info *vi)
>   {
>   	int i;
>   
> -	for (i = 0; i < vi->max_queue_pairs; i++)
> +	for (i = 0; i < vi->max_queue_pairs; i++) {
> +		virtnet_rq_init_lock(&vi->rq[i]);
>   		virtnet_napi_enable(&vi->rq[i]);
> +	}
>   }
>   
>   static void virtnet_napi_disable_all(struct virtnet_info *vi)
>   {
>   	int i;
>   
> -	for (i = 0; i < vi->max_queue_pairs; i++)
> +	for (i = 0; i < vi->max_queue_pairs; i++) {
>   		napi_disable(&vi->rq[i].napi);
> +		while (!virtnet_rq_disable(&vi->rq[i])) {
> +			pr_info("RQ %d locked\n", i);
> +			usleep_range(1000, 20000);
> +		}
> +	}
>   }
>   
>   static int virtnet_open(struct net_device *dev)
> @@ -1372,6 +1550,9 @@ static const struct net_device_ops virtnet_netdev = {
>   #ifdef CONFIG_NET_POLL_CONTROLLER
>   	.ndo_poll_controller = virtnet_netpoll,
>   #endif
> +#ifdef CONFIG_NET_RX_BUSY_POLL
> +	.ndo_busy_poll		= virtnet_low_latency_recv,
> +#endif
>   };
>   
>   static void virtnet_config_changed_work(struct work_struct *work)
> @@ -1577,6 +1758,7 @@ static int virtnet_alloc_queues(struct virtnet_info
*vi)
>   		vi->rq[i].pages = NULL;
>   		netif_napi_add(vi->dev, &vi->rq[i].napi, virtnet_poll,
>   			       napi_weight);
> +		napi_hash_add(&vi->rq[i].napi);
>   
>   		sg_init_table(vi->rq[i].sg, ARRAY_SIZE(vi->rq[i].sg));
>   		ewma_init(&vi->rq[i].mrg_avg_pkt_len, 1, RECEIVE_AVG_WEIGHT);
> @@ -1880,8 +2062,10 @@ static int virtnet_freeze(struct virtio_device
*vdev)
>   
>   	if (netif_running(vi->dev)) {
>   		virtnet_napi_disable_all(vi);
> -		for (i = 0; i < vi->max_queue_pairs; i++)
> +		for (i = 0; i < vi->max_queue_pairs; i++) {
> +			napi_hash_del(&vi->rq[i].napi);
>   			netif_napi_del(&vi->rq[i].napi);
> +		}
>   	}
>   
>   	remove_vq_common(vi);

-- 
Regards,
Varka Bhadram.

Jason Wang

2014-Jul-17 02:55 UTC

head link

[PATCH net-next V2 3/3] virtio-net: rx busy polling support

On 07/16/2014 04:38 PM, Varka Bhadram wrote:> On 07/16/2014 11:51 AM, Jason Wang wrote:
>> Add basic support for rx busy polling.
>>
>> Test was done between a kvm guest and an external host. Two hosts were
>> connected through 40gb mlx4 cards. With both busy_poll and busy_read
>> are set to 50 in guest, 1 byte netperf tcp_rr shows 116% improvement:
>> transaction rate was increased from 9151.94 to 19787.37.
>>
>> Cc: Rusty Russell <rusty at rustcorp.com.au>
>> Cc: Michael S. Tsirkin <mst at redhat.com>
>> Cc: Vlad Yasevich <vyasevic at redhat.com>
>> Cc: Eric Dumazet <eric.dumazet at gmail.com>
>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>> ---
>>   drivers/net/virtio_net.c | 190
>> ++++++++++++++++++++++++++++++++++++++++++++++-
>>   1 file changed, 187 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>> index e417d93..4830713 100644
>> --- a/drivers/net/virtio_net.c
>> +++ b/drivers/net/virtio_net.c
>> @@ -27,6 +27,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/cpu.h>
>>   #include <linux/average.h>
>> +#include <net/busy_poll.h>
>>     static int napi_weight = NAPI_POLL_WEIGHT;
>>   module_param(napi_weight, int, 0444);
>> @@ -94,8 +95,143 @@ struct receive_queue {
>>         /* Name of this receive queue: input.$index */
>>       char name[40];
>> +
>> +#ifdef CONFIG_NET_RX_BUSY_POLL
>> +    unsigned int state;
>> +#define VIRTNET_RQ_STATE_IDLE        0
>> +#define VIRTNET_RQ_STATE_NAPI         1    /* NAPI or refill owns
>> this RQ */
>> +#define VIRTNET_RQ_STATE_POLL         2    /* poll owns this RQ */
>> +#define VIRTNET_RQ_STATE_DISABLED    4    /* RQ is disabled */
>> +#define VIRTNET_RQ_OWNED (VIRTNET_RQ_STATE_NAPI |
>> VIRTNET_RQ_STATE_POLL)
>> +#define VIRTNET_RQ_LOCKED (VIRTNET_RQ_OWNED |
>> VIRTNET_RQ_STATE_DISABLED)
>> +#define VIRTNET_RQ_STATE_NAPI_YIELD  8    /* NAPI or refill yielded
>> this RQ */
>> +#define VIRTNET_RQ_STATE_POLL_YIELD  16   /* poll yielded this RQ */
>> +    spinlock_t lock;
>> +#endif  /* CONFIG_NET_RX_BUSY_POLL */
>>   };
>>   +#ifdef CONFIG_NET_RX_BUSY_POLL
>> +static inline void virtnet_rq_init_lock(struct receive_queue *rq)
>> +{
>> +
>> +    spin_lock_init(&rq->lock);
>> +    rq->state = VIRTNET_RQ_STATE_IDLE;
>> +}
>> +
>> +/* called from the device poll routine or refill routine to get
>> ownership of a
>> + * receive queue.
>> + */
>> +static inline bool virtnet_rq_lock_napi_refill(struct receive_queue
>> *rq)
>> +{
>> +    int rc = true;
>> +
>
> bool instead of int...?
Yes, it was better.>
>> +    spin_lock(&rq->lock);
>> +    if (rq->state & VIRTNET_RQ_LOCKED) {
>> +        WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
>> +        rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
>> +        rc = false;
>> +    } else
>> +        /* we don't care if someone yielded */
>> +        rq->state = VIRTNET_RQ_STATE_NAPI;
>> +    spin_unlock(&rq->lock);
>
> Lock for rq->state ...?
>
> If yes:
> spin_lock(&rq->lock);
> if (rq->state & VIRTNET_RQ_LOCKED) {
>     rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
>     spin_unlock(&rq->lock);
>     WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
>     rc = false;
> } else {
>     /* we don't care if someone yielded */
>     rq->state = VIRTNET_RQ_STATE_NAPI;
>     spin_unlock(&rq->lock);
> } 
I didn't see any differences. Is this used to catch the bug of driver
earlier? btw, several other rx busy polling capable driver does the same
thing.

Varka Bhadram

2014-Jul-17 03:27 UTC

head link

[PATCH net-next V2 3/3] virtio-net: rx busy polling support

On Thursday 17 July 2014 08:25 AM, Jason Wang wrote:> On 07/16/2014 04:38 PM, Varka Bhadram wrote:
>> On 07/16/2014 11:51 AM, Jason Wang wrote:
>>> Add basic support for rx busy polling.
>>>
>>> Test was done between a kvm guest and an external host. Two hosts
were
>>> connected through 40gb mlx4 cards. With both busy_poll and
busy_read
>>> are set to 50 in guest, 1 byte netperf tcp_rr shows 116%
improvement:
>>> transaction rate was increased from 9151.94 to 19787.37.
>>>
>>> Cc: Rusty Russell <rusty at rustcorp.com.au>
>>> Cc: Michael S. Tsirkin <mst at redhat.com>
>>> Cc: Vlad Yasevich <vyasevic at redhat.com>
>>> Cc: Eric Dumazet <eric.dumazet at gmail.com>
>>> Signed-off-by: Jason Wang <jasowang at redhat.com>
>>> ---
>>>    drivers/net/virtio_net.c | 190
>>> ++++++++++++++++++++++++++++++++++++++++++++++-
>>>    1 file changed, 187 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/virtio_net.c b/drivers/net/virtio_net.c
>>> index e417d93..4830713 100644
>>> --- a/drivers/net/virtio_net.c
>>> +++ b/drivers/net/virtio_net.c
>>> @@ -27,6 +27,7 @@
>>>    #include <linux/slab.h>
>>>    #include <linux/cpu.h>
>>>    #include <linux/average.h>
>>> +#include <net/busy_poll.h>
>>>      static int napi_weight = NAPI_POLL_WEIGHT;
>>>    module_param(napi_weight, int, 0444);
>>> @@ -94,8 +95,143 @@ struct receive_queue {
>>>          /* Name of this receive queue: input.$index */
>>>        char name[40];
>>> +
>>> +#ifdef CONFIG_NET_RX_BUSY_POLL
>>> +    unsigned int state;
>>> +#define VIRTNET_RQ_STATE_IDLE        0
>>> +#define VIRTNET_RQ_STATE_NAPI         1    /* NAPI or refill owns
>>> this RQ */
>>> +#define VIRTNET_RQ_STATE_POLL         2    /* poll owns this RQ */
>>> +#define VIRTNET_RQ_STATE_DISABLED    4    /* RQ is disabled */
>>> +#define VIRTNET_RQ_OWNED (VIRTNET_RQ_STATE_NAPI |
>>> VIRTNET_RQ_STATE_POLL)
>>> +#define VIRTNET_RQ_LOCKED (VIRTNET_RQ_OWNED |
>>> VIRTNET_RQ_STATE_DISABLED)
>>> +#define VIRTNET_RQ_STATE_NAPI_YIELD  8    /* NAPI or refill
yielded
>>> this RQ */
>>> +#define VIRTNET_RQ_STATE_POLL_YIELD  16   /* poll yielded this RQ
*/
>>> +    spinlock_t lock;
>>> +#endif  /* CONFIG_NET_RX_BUSY_POLL */
>>>    };
>>>    +#ifdef CONFIG_NET_RX_BUSY_POLL
>>> +static inline void virtnet_rq_init_lock(struct receive_queue *rq)
>>> +{
>>> +
>>> +    spin_lock_init(&rq->lock);
>>> +    rq->state = VIRTNET_RQ_STATE_IDLE;
>>> +}
>>> +
>>> +/* called from the device poll routine or refill routine to get
>>> ownership of a
>>> + * receive queue.
>>> + */
>>> +static inline bool virtnet_rq_lock_napi_refill(struct
receive_queue
>>> *rq)
>>> +{
>>> +    int rc = true;
>>> +
>> bool instead of int...?
> Yes, it was better.
>>> +    spin_lock(&rq->lock);
>>> +    if (rq->state & VIRTNET_RQ_LOCKED) {
>>> +        WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
>>> +        rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
>>> +        rc = false;
>>> +    } else
>>> +        /* we don't care if someone yielded */
>>> +        rq->state = VIRTNET_RQ_STATE_NAPI;
>>> +    spin_unlock(&rq->lock);
>> Lock for rq->state ...?
>>
>> If yes:
>> spin_lock(&rq->lock);
>> if (rq->state & VIRTNET_RQ_LOCKED) {
>>      rq->state |= VIRTNET_RQ_STATE_NAPI_YIELD;
>>      spin_unlock(&rq->lock);
>>      WARN_ON(rq->state & VIRTNET_RQ_STATE_NAPI);
>>      rc = false;
>> } else {
>>      /* we don't care if someone yielded */
>>      rq->state = VIRTNET_RQ_STATE_NAPI;
>>      spin_unlock(&rq->lock);
>> }
> I didn't see any differences. Is this used to catch the bug of driver
> earlier? btw, several other rx busy polling capable driver does the same
> thing.
We need not to include WARN_ON() & rc=false under critical section.

-- 
Regards,
Varka Bhadram

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