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05cb8b39ca
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
520ac30f45 ("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 <pabeni@redhat.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.