The network stack have some use-cases that puts some extreme demands on the memory allocator. One use-case, 10Gbit/s wirespeed at smallest packet size[1], requires handling a packet every 67.2 ns (nanosec).
Micro benchmarking[2] the SLUB allocator (with skb size 256bytes elements), show "fast-path" instant reuse only costs 19 ns, but a closer to network usage pattern show the cost rise to 45 ns. This patchset introduce a quick mempool (qmempool), which when used in-front of the SKB (sk_buff) kmem_cache, saves 12 ns on "fast-path" drop in iptables "raw" table, but more importantly saves 40 ns with IP-forwarding, which were hitting the slower SLUB use-case. One of the building blocks for achieving this speedup is a cmpxchg based Lock-Free queue that supports bulking, named alf_queue for Array-based Lock-Free queue. By bulking elements (pointers) from the queue, the cost of the cmpxchg (approx 8 ns) is amortized over several elements. Patch1: alf_queue (Lock-Free queue) Patch2: qmempool using alf_queue Patch3: usage of qmempool for SKB caching Notice, this patchset depend on introduction of napi_alloc_skb(), which is part of Alexander Duyck's work patchset [3]. Different correctness tests and micro benchmarks are avail via my github repo "prototype-kernel"[4], where the alf_queue and qmempool is also kept in sync with this patchset. Links: [1]: http://netoptimizer.blogspot.dk/2014/05/the-calculations-10gbits-wirespeed.html [2]: https://github.com/netoptimizer/prototype-kernel/blob/master/kernel/mm/qmempool_bench.c [3]: http://thread.gmane.org/gmane.linux.network/342347 [4]: https://github.com/netoptimizer/prototype-kernel --- Jesper Dangaard Brouer (3): net: use qmempool in-front of sk_buff kmem_cache mm: qmempool - quick queue based memory pool lib: adding an Array-based Lock-Free (ALF) queue include/linux/alf_queue.h | 303 ++++++++++++++++++++++++++++++++++++++++++ include/linux/qmempool.h | 205 +++++++++++++++++++++++++++++ include/linux/skbuff.h | 4 - lib/Kconfig | 13 ++ lib/Makefile | 2 lib/alf_queue.c | 47 +++++++ mm/Kconfig | 12 ++ mm/Makefile | 1 mm/qmempool.c | 322 +++++++++++++++++++++++++++++++++++++++++++++ net/core/dev.c | 5 + net/core/skbuff.c | 43 +++++- 11 files changed, 950 insertions(+), 7 deletions(-) create mode 100644 include/linux/alf_queue.h create mode 100644 include/linux/qmempool.h create mode 100644 lib/alf_queue.c create mode 100644 mm/qmempool.c -- Best regards, Jesper Dangaard Brouer MSc.CS, Sr. Network Kernel Developer at Red Hat Author of http://www.iptv-analyzer.org LinkedIn: http://www.linkedin.com/in/brouer -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
