On Thu, Jan 30, 2014 at 07:08:11PM +0000, Zoltan Kiss wrote: > Hi, > > I've experienced some queue timeout problems mentioned in the > subject with igb and bnx2 cards. I haven't seen them on other cards > so far. I'm using XenServer with 3.10 Dom0 kernel (however igb were > already updated to latest version), and there are Windows guests > sending data through these cards. I noticed these problems in XenRT > test runs, and I know that they usually mean some lost interrupt > problem or other hardware error, but in my case they started to > appear more often, and they are likely connected to my netback grant > mapping patches. These patches causing skb's with huge (~64kb) > linear buffers to appear more often. > The reason for that is an old problem in the ring protocol: > originally the maximum amount of slots were linked to MAX_SKB_FRAGS, > as every slot ended up as a frag of the skb. When this value were > changed, netback had to cope with the situation by coalescing the > packets into fewer frags. > My patch series take a different approach: the leftover slots > (pages) were assigned to a new skb's frags, and that skb were > stashed to the frag_list of the first one. Then, before sending it > off to the stack it calls skb = skb_copy_expand(skb, 0, 0, > GFP_ATOMIC, __GFP_NOWARN), which basically creates a new skb and > copied all the data into it. As far as I understood, it put > everything into the linear buffer, which can amount to 64KB at most. > The original skb are freed then, and this new one were sent to the > stack.
Just my two cents, if it is this case, you can try to call skb_copy_expand on every SKB netback receives to manually create SKBs with ~64KB linear buffer to see how it goes... Wei. > I suspect that this is the problem as it only happens when guests > send too much slots. Does anyone familiar with these drivers have > seen such issue before? (when these kind of skb's get stucked in the > queue) > > Regards, > > Zoltan Kiss > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/