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[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: Santiago Leon <santil@us.ibm.com>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
This commit is contained in:
Santiago Leon 2005-10-26 10:47:08 -06:00 committed by Jeff Garzik
parent b6d35182fe
commit e2adbcb480
2 changed files with 8 additions and 44 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

48
drivers/net/ibmveth.c
View File

@ -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);

4
drivers/net/ibmveth.h
View File

@ -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;