RFC Faster than SLAB caching of SKBs with qmempool (backed by alf_queue)
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b4 am 20141210141332.31779.56391.stgit@dragonVersions newest first
- v1 RFC Latest3 patches 8 repliesIn review
Patches in v1 No applies recorded yet
| # | Subject and files | Size | Replies | Applied |
|---|---|---|---|---|
| 1/3 | lib: adding an Array-based Lock-Free (ALF) queueinclude/ lib/ lib/ +1 more | +365 | 1 reply | |
| 2/3 | mm: qmempool - quick queue based memory poolinclude/ mm/ mm/ +1 more | +540 | 0 replies | |
| 3/3 | net: use qmempool in-front of sk_buff kmem_cacheinclude/ net/ net/ | +45 | 0 replies |
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Cover letter [RFC PATCH 0/3] Faster than SLAB caching of SKBs with qmempool (backed by alf_queue)
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
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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
Signature · 11 lines
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, send a message with 'unsubscribe linux-mm' in the body to [email protected]. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"[email protected]"> [email protected] </a>