Commit e2adbcb4 authored by Santiago Leon's avatar Santiago Leon Committed by Jeff Garzik
Browse files

[PATCH] ibmveth fix buffer replenishing 



This patch removes the allocation of RX skb's  buffers from a workqueue
to be called directly at RX processing time.  This change was suggested
by Dave Miller when the driver was starving the RX buffers and
deadlocking under heavy traffic:

> Allocating RX SKBs via tasklet is, IMHO, the worst way to
> do it.  It is no surprise that there are starvation cases.
>
> If tasklets or work queues get delayed in any way, you lose,
> and it's very easy for a card to catch up with the driver RX'ing
> packets very fast, no matter how aggressive you make the
> replenishing.  By the time you detect that you need to be
> "more aggressive" it is already too late.
> The only pseudo-reliable way is to allocate at RX processing time.
>

Signed-off-by: default avatarSantiago Leon <santil@us.ibm.com>
Signed-off-by: default avatarJeff Garzik <jgarzik@pobox.com>
parent b6d35182

drivers/net/ibmveth.c

+8 −40
Original line number Diff line number Diff line
@@ -96,7 +96,6 @@ static void ibmveth_proc_unregister_driver(void); 
static void ibmveth_proc_register_adapter(struct ibmveth_adapter *adapter);

static void ibmveth_proc_unregister_adapter(struct ibmveth_adapter *adapter);

static irqreturn_t ibmveth_interrupt(int irq, void *dev_instance, struct pt_regs *regs);

static inline void ibmveth_schedule_replenishing(struct ibmveth_adapter*);

static inline void ibmveth_rxq_harvest_buffer(struct ibmveth_adapter *adapter);



#ifdef CONFIG_PROC_FS
@@ -257,29 +256,7 @@ static void ibmveth_replenish_buffer_pool(struct ibmveth_adapter *adapter, struc 
	atomic_add(buffers_added, &(pool->available));

}



/* check if replenishing is needed.  */

static inline int ibmveth_is_replenishing_needed(struct ibmveth_adapter *adapter)

{

	int i;



	for(i = 0; i < IbmVethNumBufferPools; i++)

		if(adapter->rx_buff_pool[i].active &&

		  (atomic_read(&adapter->rx_buff_pool[i].available) <

		   adapter->rx_buff_pool[i].threshold))

			return 1;

	return 0;

}



/* kick the replenish tasklet if we need replenishing and it isn't already running */

static inline void ibmveth_schedule_replenishing(struct ibmveth_adapter *adapter)

{

	if(ibmveth_is_replenishing_needed(adapter) &&

	   (atomic_dec_if_positive(&adapter->not_replenishing) == 0)) {

		schedule_work(&adapter->replenish_task);

	}

}



/* replenish tasklet routine */

/* replenish routine */

static void ibmveth_replenish_task(struct ibmveth_adapter *adapter) 

{

	int i;
@@ -292,10 +269,6 @@ static void ibmveth_replenish_task(struct ibmveth_adapter *adapter) 
						     &adapter->rx_buff_pool[i]);



	adapter->rx_no_buffer = *(u64*)(((char*)adapter->buffer_list_addr) + 4096 - 8);



	atomic_inc(&adapter->not_replenishing);



	ibmveth_schedule_replenishing(adapter);

}



/* empty and free ana buffer pool - also used to do cleanup in error paths */
@@ -563,10 +536,10 @@ static int ibmveth_open(struct net_device *netdev) 
		return rc;

	}



	netif_start_queue(netdev);

	ibmveth_debug_printk("initial replenish cycle\n");

	ibmveth_replenish_task(adapter);



	ibmveth_debug_printk("scheduling initial replenish cycle\n");

	ibmveth_schedule_replenishing(adapter);

	netif_start_queue(netdev);



	ibmveth_debug_printk("open complete\n");
@@ -584,9 +557,6 @@ static int ibmveth_close(struct net_device *netdev) 


	free_irq(netdev->irq, netdev);



	cancel_delayed_work(&adapter->replenish_task);

	flush_scheduled_work();



	do {

		lpar_rc = h_free_logical_lan(adapter->vdev->unit_address);

	} while (H_isLongBusy(lpar_rc) || (lpar_rc == H_Busy));
@@ -795,7 +765,7 @@ static int ibmveth_poll(struct net_device *netdev, int *budget) 
		}

	} while(more_work && (frames_processed < max_frames_to_process));



	ibmveth_schedule_replenishing(adapter);

	ibmveth_replenish_task(adapter);



	if(more_work) {

		/* more work to do - return that we are not done yet */
@@ -931,8 +901,10 @@ static int ibmveth_change_mtu(struct net_device *dev, int new_mtu) 


	}



	/* kick the interrupt handler so that the new buffer pools get

	   replenished or deallocated */

	ibmveth_interrupt(dev->irq, dev, NULL);



	ibmveth_schedule_replenishing(adapter);

	dev->mtu = new_mtu;

	return 0;	

}
@@ -1017,14 +989,10 @@ static int __devinit ibmveth_probe(struct vio_dev *dev, const struct vio_device_ 


	ibmveth_debug_printk("adapter @ 0x%p\n", adapter);



	INIT_WORK(&adapter->replenish_task, (void*)ibmveth_replenish_task, (void*)adapter);



	adapter->buffer_list_dma = DMA_ERROR_CODE;

	adapter->filter_list_dma = DMA_ERROR_CODE;

	adapter->rx_queue.queue_dma = DMA_ERROR_CODE;



	atomic_set(&adapter->not_replenishing, 1);



	ibmveth_debug_printk("registering netdev...\n");



	rc = register_netdev(netdev);

drivers/net/ibmveth.h

+0 −4
Original line number Diff line number Diff line
@@ -118,10 +118,6 @@ struct ibmveth_adapter { 
    dma_addr_t filter_list_dma;

    struct ibmveth_buff_pool rx_buff_pool[IbmVethNumBufferPools];

    struct ibmveth_rx_q rx_queue;

    atomic_t not_replenishing;



    /* helper tasks */

    struct work_struct replenish_task;



    /* adapter specific stats */

    u64 replenish_task_cycles;

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