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authorjaszha03 <jason.zhang2@arm.com>2019-07-01 17:08:57 -0500
committerFlorin Coras <florin.coras@gmail.com>2019-08-01 18:01:33 +0000
commit30aaf97a90230d68c0f2736b0a026e07b06e7e32 (patch)
treefcfa22ff97deab6c60be759f183b2fcab92c6210 /docs/gettingstarted/developers
parent691a3b7f11c41851d747e35c6bc5db9319d92c20 (diff)
vppinfra: refactor clib_rwlock_t to use single condition variable
Previous implementation of clib_rwlock_t used two spinlocks: one writer lock, and one to guard the counter for the number of readers. This implementation uses a single condition variable rw_cnt which has the following properties: if a writer has the rwlock, rw_cnt = -1 if the rwlock is free, rw_cnt = 0 otherwise, rw_cnt > 0 and rw_cnt = number of readers rw_cnt will never be less than -1 Benchmarking: The results below are the cycle counts from test_rwlock.c, configured so that for 10000 iterations, 6 reader and 6 writer threads on separate cores are spawned such that each writer thread increments a global counter 10000 times in each iteration. For Taishan, 4 reader and 4 writer threads are spawned in each test. x86 Xeon old rwlock: 12.473e8, 11.655e8, 13.201e8, 11.347e8, 13.182e8 x86 Xeon new rwlock: 5.881e8, 5.796e8, 6.536e8, 5.540e8, 5.890e8 Aarch64 ThX2* old rwlock: 9.263e7, 8.933e7, 9.074e7, 8.979e7, 9.378e7 Aarch64 ThX2* new rwlock: 7.221e7, 8.107e7, 7.515e7, 7.672e7, 7.386e7 A72 old rwlock: 3.268e6, 3.200e6, 3.086e6, 3.176e6, 3.170e6 A72 new rwlock: 1.261e6, 1.288e6, 1.251e6, 1.229e6, 1.234e6 *ThunderX2 used additional gcc options "-march=armv8.1-a+crc+crypto+lse" Type: refactor Change-Id: I7c347d3037b36205ab532cbcb52a374c846eb275 Signed-off-by: Jason Zhang <jason.zhang2@arm.com> Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com> Reviewed-by: Lijian Zhang <Lijian.Zhang@arm.com>
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