From: David S. Miller (davem@xxxxxxxxxxxxx)
Sent: Tue, 23 May 2017 11:26:25 -0400
> From: Oliver Neukum <oneukum@xxxxxxxx>
> Date: Tue, 23 May 2017 10:42:48 +0200
>
>>
>> We could use a counter. After the first failure, do it once, after the
>> second twice and so on. And reset the counter as a higher order
>> allocation works. (just bound it somewhere)
>
> So an exponential backoff, that might work.
>
As an idea I have created this patch as an addition to the original patch
in this series.
Would this be acceptable?
At the moment I have capped the value at 10, does anyone think it needs to
be much higher then that?
Regards,
Jim
diff --git a/drivers/net/usb/cdc_ncm.c b/drivers/net/usb/cdc_ncm.c
index c06d20f..0e40603 100644
--- a/drivers/net/usb/cdc_ncm.c
+++ b/drivers/net/usb/cdc_ncm.c
@@ -89,6 +89,8 @@ struct cdc_ncm_stats {
CDC_NCM_SIMPLE_STAT(rx_ntbs),
};
+#define CDC_NCM_LOW_MEM_MAX_CNT 10
+
static int cdc_ncm_get_sset_count(struct net_device __always_unused *netdev, int sset)
{
switch (sset) {
@@ -1111,8 +1113,13 @@ struct sk_buff *
/* allocate a new OUT skb */
if (!skb_out) {
- ctx->tx_curr_size = ctx->tx_max;
- skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);
+ if (ctx->tx_low_mem_val == 0) {
+ ctx->tx_curr_size = ctx->tx_max;
+ skb_out = alloc_skb(ctx->tx_curr_size, GFP_ATOMIC);
+ if (skb_out == NULL) {
+ ctx->tx_low_mem_max_cnt = min(ctx->tx_low_mem_max_cnt + 1, CDC_NCM_LOW_MEM_MAX_CNT);
+ ctx->tx_low_mem_val = ctx->tx_low_mem_max_cnt;
+ }
if (skb_out == NULL) {
/* See if a very small allocation is possible.
* We will send this packet immediately and hope
@@ -1127,12 +1134,13 @@ struct sk_buff *
/* No allocation possible so we will abort */
if (skb_out == NULL) {
- if (skb != NULL) {
+ if (skb) {
dev_kfree_skb_any(skb);
dev->net->stats.tx_dropped++;
}
goto exit_no_skb;
}
+ ctx->tx_low_mem_val--;
}
/* fill out the initial 16-bit NTB header */
nth16 = (struct usb_cdc_ncm_nth16 *)memset(skb_put(skb_out, sizeof(struct usb_cdc_ncm_nth16)), 0, sizeof(struct usb_cdc_ncm_nth16));
diff --git a/include/linux/usb/cdc_ncm.h b/include/linux/usb/cdc_ncm.h
index 5162f38..25a0aed 100644
--- a/include/linux/usb/cdc_ncm.h
+++ b/include/linux/usb/cdc_ncm.h
@@ -118,6 +118,8 @@ struct cdc_ncm_ctx {
u32 rx_max;
u32 tx_max;
u32 tx_curr_size;
+ u32 tx_low_mem_max_cnt;
+ u32 tx_low_mem_val;
u32 max_datagram_size;
u16 tx_max_datagrams;
u16 tx_remainder;
--
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