netdev - Re: [PATCH v3 4/4] USBNET: ax88179_178a: enable tso if usb host supports sg dma

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 6 Aug 2013 23:07:20 +0800
From:	Ming Lei <ming.lei@...onical.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Oliver Neukum <oneukum@...e.de>,
	Sarah Sharp <sarah.a.sharp@...ux.intel.com>,
	netdev@...r.kernel.org, linux-usb@...r.kernel.org,
	Ben Hutchings <bhutchings@...arflare.com>,
	Grant Grundler <grundler@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Freddy Xin <freddy@...x.com.tw>
Subject: Re: [PATCH v3 4/4] USBNET: ax88179_178a: enable tso if usb host
 supports sg dma

On Tue, Aug 6, 2013 at 8:22 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> On Tue, 2013-08-06 at 08:52 +0800, Ming Lei wrote:
>> This patch enables 'can_dma_sg' flag for ax88179_178a device
>> if the attached host controller supports building packet from
>> discontinuous buffers(DMA SG is possible), so TSO can be enabled
>> and skb fragment buffers can be passed to usb stack via urb->sg
>> directly.
>>
>> With the patch, system CPU utilization decreased ~50% and throughput
>> increased by ~10% when doing iperf client test on one ARM A15 dual
>> core board.
>>
>
> Nice ;)
>
>>              AX_RXCOE_TCPV6 | AX_RXCOE_UDPV6;
>> @@ -1310,6 +1318,10 @@ static int ax88179_reset(struct usbnet *dev)
>>
>>       dev->net->hw_features |= NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
>>                                NETIF_F_RXCSUM;
>> +     if (dev->can_dma_sg) {
>> +             dev->net->features |= NETIF_F_SG | NETIF_F_TSO;
>> +             dev->net->hw_features |= NETIF_F_SG | NETIF_F_TSO;
>> +     }
>>
>
> My concern with setting TSO on reset() is the following :
>
> Admin can disable TSO with
>
> ethtool -K ethX tso off
>
>
> Then, one hour later, or one month later, a reset happens, and this code
> magically re-enables TSO

The reset only happens during open(), and TSO can't be re-enabled magically,
unless the interface is re-opened by Admin.

>
> So, I really think this part should be removed from your patch.

OK, will remove it.


Thanks,
--
Ming Lei
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html