On 08/20/2015 04:53 PM, Grumbach, Emmanuel wrote: > > > On 08/20/2015 04:11 PM, Eric Dumazet wrote: >> On Thu, 2015-08-20 at 06:21 +0000, Grumbach, Emmanuel wrote: >>> >>> On 08/19/2015 11:39 PM, Eric Dumazet wrote: >>>> On Wed, 2015-08-19 at 19:17 +0000, Grumbach, Emmanuel wrote: >>>> >>>>> Hm.. how would net/core/tso.c avoid this? >>>> >>>> Because a driver using these helpers keep around the original LSO packet >>>> and frees it normally at TX completion time. >>>> >>> >>> Which is why I can't really use it. The complexity is that I have to >>> (ieee802.11 specification) split an LSO is several 802.11 packets. The >>> maximal 802.11 packet I can send under ideal condition is 11K long or >>> so. So I *must* generate several 802.11 frames from one single LSO >>> packet. OTOH, I can have more than MSS bytes in a 802.11 A-MSDU. >>> >> >> Who said you had to free original packet ? Just keep it around. >> >> TCP will work better ( check skb_still_in_host_queue() helper if you >> want to know why) > > I do keep the original skb: it becomes the first 802.11 packet generated > from that LSO skb. Thing is that it will be freed first and I wanted the > *last packet* to release the pressure on the socket. > So I guess that skb_still_in_host_queue will still find it and avoid > retransmissions at least until the first skb of the LSO is freed. > But unless you are fine with releasing the pressing on the socket as > soon as the *first* 802.11 skb is freed, I need that code. > > I'll try to look at dev->gso_max_size that you mentioned below. This can > really be a game changer for me. > Err... no :( It won't work for me because the MSS impacts the number of segments which in turns impact the number of time the headers have to be copied which impacts... the A-MSDU maximal size which must be bigger than gso_max_size. So basically, a connection parameter (MSS) impacts a device parameter (gso_max_size). Now, of course, I could give up on small MSS connections and skb_gso_segment() skbs whose MSS is smaller than the default. This means that I give up on LSO in certain cases... I will get back to the drawing board and check what I can do to use / enhance the core infra... But it will be hard to lose functionality / efficiency just to use the core infra... -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
