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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. This patches create a stack local array with SKBs to bulk free while walking the list. Bulk array size is limited to 16 SKBs to trade off stack usage and efficiency. The SLUB kmem_cache "skbuff_head_cache" uses objsize 256 bytes usually in an order-1 page 8192 bytes that is 32 objects per slab (can vary on archs and due to SLUB sharing). Thus, for SLUB the optimal bulk free case is 32 objects belonging to same slab, but runtime this isn't likely to occur. The expected gain from using kmem_cache bulk alloc and free API have been assessed via a microbencmark kernel module[1]. The module 'slab_bulk_test01' results at bulk 16 element: kmem-in-loop Per elem: 109 cycles(tsc) 30.532 ns (step:16) kmem-bulk Per elem: 64 cycles(tsc) 17.905 ns (step:16) More detailed description of benchmarks avail in [2]. [1] https://github.com/netoptimizer/prototype-kernel/tree/master/kernel/mm [2] https://github.com/xdp-project/xdp-project/blob/master/areas/mem/kfree_skb_list01.org V2: rename function to kfree_skb_add_bulk. Reviewed-by: Saeed Mahameed <saeed@kernel.org> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com> 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.