On Wed, Apr 22, 2015 at 8:37 PM, Pravin Shelar <pshe...@nicira.com> wrote: > On Wed, Apr 22, 2015 at 8:29 PM, Jesse Gross <je...@nicira.com> wrote: >> 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. > > If destructor is replicated on the individual skbs then it will be > called for each of those skbs when it is freed.
Right; if we've correctly apportioned truesize among the individual skbs isn't that the goal? _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev