Hi Jonathan, On Mar 22, 2015, at 11:43 , Jonathan Morton <[email protected]> wrote:
> >> On 22 Mar, 2015, at 11:39, Sebastian Moeller <[email protected]> wrote: >> >> I could be out to lunch here, as usual,;but I argue the byte limit should >> include the kernel overhead (could this be based on skb->truesize) as this >> is what counts against real memory. My assumption here is that in normal >> operation we rarely/never get queues to fill up to the limit anyways > > Such an argument could certainly be made. Does skb->truesize include the skb > header, as well as the buffer space allocated? According to http://vger.kernel.org/~davem/skb_sk.html (“We keep track of how many bytes of system memory are consumed by a packet in 'skb->truesize'. This is the total of how large a data buffer we allocated for the packet, plus the size of 'struct sk_buff' itself.") it looks like this should be the right number, but I am not well versed in reading kernel code, so there might be some caveats I am not aware of. > >> (as tho would turn the queue into tail-drop effectively) > > But fq_codel (and cake) are a little cleverer than that, even when they hit > the hard limit. They still drop from the head, and they shoot the longest > flow-queue first. Excellent, learned something new today; in fq_codel does this come from the per-codel instance 1000 packet limit or from the default fq_codel 102400? packet limit (just in case someone knows off hand, I can try to understand the kernel code myself, given enough time ;) )? Best Regards Sebastian > > - Jonathan Morton > _______________________________________________ Codel mailing list [email protected] https://lists.bufferbloat.net/listinfo/codel
