On Wed, Apr 22, 2015 at 8:22 PM, Pravin Shelar <pshe...@nicira.com> wrote: > On Wed, Apr 22, 2015 at 7:48 PM, Jesse Gross <je...@nicira.com> wrote: >> On Wed, Apr 22, 2015 at 3:38 PM, Pravin Shelar <pshe...@nicira.com> wrote: >>> On Wed, Apr 22, 2015 at 3:24 PM, Jesse Gross <je...@nicira.com> wrote: >>>> On Wed, Apr 22, 2015 at 3:19 PM, Pravin Shelar <pshe...@nicira.com> wrote: >>>>> On Wed, Apr 22, 2015 at 11:31 AM, Jesse Gross <je...@nicira.com> wrote: >>>>>> On Wed, Apr 22, 2015 at 11:09 AM, Pravin Shelar <pshe...@nicira.com> >>>>>> wrote: >>>>>>> On Wed, Apr 22, 2015 at 10:52 AM, Jesse Gross <je...@nicira.com> wrote: >>>>>>>> On Wed, Apr 22, 2015 at 10:03 AM, Pravin Shelar <pshe...@nicira.com> >>>>>>>> wrote: >>>>>>>>> On Mon, Apr 20, 2015 at 9:54 PM, Jesse Gross <je...@nicira.com> wrote: >>>>>>>>>> On Mon, Apr 20, 2015 at 7:33 PM, Pravin Shelar <pshe...@nicira.com> >>>>>>>>>> wrote: >>>>>>>>>>> On Mon, Apr 20, 2015 at 5:56 PM, Jesse Gross <je...@nicira.com> >>>>>>>>>>> wrote: >>>>>>>>>>>> On Mon, Apr 20, 2015 at 3:54 PM, Pravin Shelar >>>>>>>>>>>> <pshe...@nicira.com> wrote: >>>>>>>>>>>>> On Mon, Apr 20, 2015 at 3:36 PM, Jesse Gross <je...@nicira.com> >>>>>>>>>>>>> wrote: >>>>>>>>>>>>>> On Mon, Apr 20, 2015 at 1:29 PM, Pravin B Shelar >>>>>>>>>>>>>> <pshe...@nicira.com> wrote: >>>>>>>>>>>>>>> diff --git a/datapath/linux/compat/stt.c >>>>>>>>>>>>>>> b/datapath/linux/compat/stt.c >>>>>>>>>>>>>>> new file mode 100644 >>>>>>>>>>>>>>> index 0000000..209bf1a >>>>>>>>>>>>>>> --- /dev/null >>>>>>>>>>>>>>> +++ b/datapath/linux/compat/stt.c >>>>>>>>>>>>>>> +static void update_headers(struct sk_buff *skb, bool head, >>>>>>>>>>>>>>> + unsigned int l4_offset, unsigned >>>>>>>>>>>>>>> int hdr_len, >>>>>>>>>>>>>>> + bool ipv4, u32 tcp_seq) >>>>>>>>>>>>>> [...] >>>>>>>>>>>>>>> + skb->truesize = SKB_TRUESIZE(skb_end_offset(skb)) + >>>>>>>>>>>>>>> skb->data_len; >>>>>>>>>>>>>>> +} >>>>>>>>>>>>>> >>>>>>>>>>>>>> I wonder if there are any possible edge cases with resetting >>>>>>>>>>>>>> truesize >>>>>>>>>>>>>> where the packet is still in someone's transmit queue (such as >>>>>>>>>>>>>> if we >>>>>>>>>>>>>> are looping back packet). Do we need to orphan it first? >>>>>>>>>>>>>> >>>>>>>>>>>>> ok, I will orphan it in update_headers. >>>>>>>>>>>> >>>>>>>>>>>> Just to clarify - I was mostly just thinking aloud on orphaning it. >>>>>>>>>>>> I'm not totally sure if that is the right thing to do or if this is >>>>>>>>>>>> the right place to do it. I'm not sure what the conceptual >>>>>>>>>>>> justification would be for it and it could potentially result in >>>>>>>>>>>> the >>>>>>>>>>>> sender's buffers not being properly limited. Perhaps not resetting >>>>>>>>>>>> the >>>>>>>>>>>> truesize is the right thing too... >>>>>>>>>>>> >>>>>>>>>>> I have seen warning msg if we do no keep truesize update along with >>>>>>>>>>> changes to skb. >>>>>>>>>> >>>>>>>>>> Hmm, interesting, what is the warning? I don't think that I have seen >>>>>>>>>> that before. >>>>>>>>> >>>>>>>>> Actually skb_try_coalesce() is updating it correctly. so there no need >>>>>>>>> to change truesize anymore. I will update patch accordingly. >>>>>>>> >>>>>>>> That's much nicer. I also checked and other receive side code (like >>>>>>>> TCP input) doesn't worry about the case where a local sender may still >>>>>>>> be accounting for the packet since any type of loopback device does >>>>>>>> call skb_orphan() in some form. >>>>>>>> >>>>>>>> I hate to bring this up but what about on transmit? In cases where we >>>>>>>> merge or split skbs (skb_try_coalesce() and normalize_frag_list() >>>>>>>> respectively) we do track the truesize for correctly for the result >>>>>>>> but the individual pieces might not have the right destructors or >>>>>>>> might not have their truesize updated for the destructor they do have. >>>>>>> >>>>>>> How about about we update merged skb stats (len, data_len, truesize) >>>>>>> according to *delta_truesize we get from skb_try_coalesce() and then >>>>>>> free the skb? >>>>>> >>>>>> I think that would work for the skb_try_coalesce() case (although I >>>>>> would only worry about truesize, not the lengths). For >>>>>> normalize_frag_list() I think we would either have to add a destructor >>>>>> or not update truesize. I'm not sure that the condition where we have >>>>>> frag_lists and a destructor actually ever happens in practice though. >>>>> >>>>> I am not sure why do we need a destructor for normalize_frag_list >>>>> changes. Even with the changes in the function truesize is consistent >>>>> for given skb memory usage. >>>> >>>> If you have a packet with a frag_list, all of the memory for the >>>> individual elements will be accounted for in the truesize in the top >>>> level skb. This skb could also be accounted to some socket and have a >>>> destructor. When we break apart the list, we remove the truesize from >>>> the head because the memory is now part of individual packets. >>>> However, the destructor is presumably only on the head and so only its >>>> memory will be removed from the socket accounting when it is freed but >>>> not each of the other skbs that came from it. >>> >>> ok. In that case we can not have our own destructor since there is one >>> already (I am not sure if we can use skb->cb to restore original). not >>> changing true size can complicate skb coalesce, since it does update >>> truesize. Easy option would be orphan skb if we are going to coalesce >>> its fragments. >> >> I'm not sure that we need our own destructor. What do you think about >> just replicating the original destructor onto each of the newly >> generated skbs? >> > In that case we assume there is no state associated with the skb, that > might not be always true.
What state do you mean? If you mean a destructor on the individual skbs, I think that is already true because only the top level destructor will get called when the original skb is freed. _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
