On Mon, 25 Mar 2019 10:35:35 +0100 Felix Fietkau <n...@nbd.name> wrote: > On 2019-03-25 10:31, Eric Dumazet wrote: > > On 03/25/2019 02:09 AM, Felix Fietkau wrote: > >> On 2019-03-25 09:51, Eric Dumazet wrote: > >>> On 03/24/2019 09:56 AM, Felix Fietkau wrote: > >>>> > >>>> Since we're freeing multiple skbs, we might as well use bulk > >>>> free to save a few cycles. Use the same conditions for bulk free > >>>> as in napi_consume_skb. > >>> > >>> I do not believe kfree_skb_list() is used in the fast path, so do > >>> we really need to make it so complex ? > >> > >> mac80211 uses it to free the fraglist from A-MSDU aggregated > >> packets in the tx status path. That's one fast path where it gets > >> used right now and the reason it was showing up in my perf > >> traces.
Notice that kfree_skb_list(to_free) is used in (what I consider) "fast-path" when the qdisc system drops packets, happens via to_free in bottom of __dev_xmit_skb(). And fq_codel (which is default in most distro's today) have an optimization (in fq_codel_drop()) for bulk freeing SKBs, which will also benefit from this. Thus, I still think it will be valuable to optimize kfree_skb_list(). > > This is not drop monitor friendly then.... > > > > TX completion should use consume_skb() or dev_kfree_skb() > > > > BTW, I wonder what drop-monitor signal bulk free is sending ? > > Good point about the drop monitor. Would you prefer that I replace > this patch with one that adds a consume_skb_list function and another > one that makes mac80211 use it? -- Best regards, Jesper Dangaard Brouer MSc.CS, Principal Kernel Engineer at Red Hat LinkedIn: http://www.linkedin.com/in/brouer
