From: Paolo Abeni Date: Tue, 17 Jan 2023 09:27:31 +0000 (+0100) Subject: Merge branch 'net-use-kmem_cache_free_bulk-in-kfree_skb_list' X-Git-Url: http://git.maquefel.me/?a=commitdiff_plain;h=05cb8b39ca59e7bc4e0810a66f59266d76e4671a;p=linux.git Merge branch 'net-use-kmem_cache_free_bulk-in-kfree_skb_list' Jesper Dangaard Brouer says: ==================== net: use kmem_cache_free_bulk in kfree_skb_list The kfree_skb_list function walks SKB (via skb->next) and frees them individually to the SLUB/SLAB allocator (kmem_cache). It is more efficient to bulk free them via the kmem_cache_free_bulk API. Netstack NAPI fastpath already uses kmem_cache bulk alloc and free APIs for SKBs. The kfree_skb_list call got an interesting optimization in commit 520ac30f4551 ("net_sched: drop packets after root qdisc lock is released") that can create a list of SKBs "to_free" e.g. when qdisc enqueue fails or deliberately chooses to drop . It isn't a normal data fastpath, but the situation will likely occur when system/qdisc are under heavy workloads, thus it makes sense to use a faster API for freeing the SKBs. E.g. the (often distro default) qdisc fq_codel will drop batches of packets from fattest elephant flow, default capped at 64 packets (but adjustable via tc argument drop_batch). Performance measurements done in [1]: [1] https://github.com/xdp-project/xdp-project/blob/master/areas/mem/kfree_skb_list01.org ==================== Link: https://lore.kernel.org/r/167361788585.531803.686364041841425360.stgit@firesoul Signed-off-by: Paolo Abeni --- 05cb8b39ca59e7bc4e0810a66f59266d76e4671a