On 2019/10/19 6:48, Jakub Kicinski wrote:
On Fri, 18 Oct 2019 06:01:25 -0400, Zhu Yanjun wrote:
This change adds support for xmit_more based on the igb commit 6f19e12f6230
("igb: flush when in xmit_more mode and under descriptor pressure") and
commit 6b16f9ee89b8 ("net: move skb->xmit_more hint to softnet data") that
were made to igb to support this feature. The function netif_xmit_stopped
is called to check if transmit queue on device is currently unable to send
to determine if we must write the tail because we can add no further
buffers.
When normal packets and/or xmit_more packets fill up tx_desc, it is
necessary to trigger NIC tx reg.
Looks broken. You gotta make sure you check the kick on _every_ return
path. There are 4 return statements in each function, you only touched
2.
In nv_start_xmit,
2240 if (unlikely(empty_slots <= entries)) {
2241 netif_stop_queue(dev);
2242 np->tx_stop = 1;
2243 spin_unlock_irqrestore(&np->lock, flags);
2244
2245 /* When normal packets and/or xmit_more packets fill up
2246 * tx_desc, it is necessary to trigger NIC tx reg.
2247 */
2248 ret = NETDEV_TX_BUSY;
2249 goto TXKICK;
2250 }
The above indicates tx_desc is full, it is necessary to trigger NIC HW xmit.
2261 if (unlikely(dma_mapping_error(&np->pci_dev->dev,
2262 np->put_tx_ctx->dma))) {
2263 /* on DMA mapping error - drop the packet */
2264 dev_kfree_skb_any(skb);
2265 u64_stats_update_begin(&np->swstats_tx_syncp);
2266 nv_txrx_stats_inc(stat_tx_dropped);
2267 u64_stats_update_end(&np->swstats_tx_syncp);
2268 return NETDEV_TX_OK;
2269 }
and
2300 if
(unlikely(dma_mapping_error(&np->pci_dev->dev,
2301 np->put_tx_ctx->dma))) {
2302
2303 /* Unwind the mapped fragments */
2304 do {
2305 nv_unmap_txskb(np,
start_tx_ctx);
2306 if (unlikely(tmp_tx_ctx++
== np->last_tx_ctx))
2307 tmp_tx_ctx =
np->tx_skb;
2308 } while (tmp_tx_ctx != np->put_tx_ctx);
2309 dev_kfree_skb_any(skb);
2310 np->put_tx_ctx = start_tx_ctx;
2311 u64_stats_update_begin(&np->swstats_tx_syncp);
2312 nv_txrx_stats_inc(stat_tx_dropped);
2313 u64_stats_update_end(&np->swstats_tx_syncp);
2314 return NETDEV_TX_OK;
2315 }
The above are dma_mapping_error. It seems that triggering NIC HW xmit is
not needed.
So when "tx_desc full" error, HW NIC xmit is triggerred. When
dma_mapping_error,
NIC HW xmit is not triggerred.
That is why only 2 "return" are touched.
Also the labels should be lower case.
This patch passes checkpatch.pl. It seems that "not lower case" is not a
problem?
If you think it is a problem, please show me where it is defined.
Zhu Yanjun
