From: Zhu Yanjun <yanjun.zhu@oracle.com>
To: Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: rain.1986.08.12@gmail.com, davem@davemloft.net, netdev@vger.kernel.org
Subject: Re: [PATCH] net: forcedeth: add xmit_more support
Date: Mon, 21 Oct 2019 17:56:06 +0800 [thread overview]
Message-ID: <84839e5f-4543-bbd9-37db-e1777a84992c@oracle.com> (raw)
In-Reply-To: <20191018154844.34a27c64@cakuba.netronome.com>
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
>
next prev parent reply other threads:[~2019-10-21 9:50 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-18 10:01 [PATCH] net: forcedeth: add xmit_more support Zhu Yanjun
2019-10-18 22:48 ` Jakub Kicinski
2019-10-21 9:56 ` Zhu Yanjun [this message]
2019-10-21 15:33 ` Jakub Kicinski
2019-10-22 5:32 ` Zhu Yanjun
2019-10-22 15:40 ` Jakub Kicinski
2019-10-23 0:45 ` Zhu Yanjun
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