This patch set is a collection of 3 different mutex related patches aimed at improving mutex performance especially for system with large number of CPUs. This is achieved by doing less atomic operations and mutex spinning (when the CONFIG_MUTEX_SPIN_ON_OWNER is on).
The first patch reduces the number of atomic operations executed. It can produce dramatic performance improvement in the AIM7 benchmark with large number of CPUs. For example, there was a more than 3X improvement in the high_systime workload with a 3.7.10 kernel on an 8-socket x86-64 system with 80 cores. The 3.8 kernels, on the other hand, are not mutex limited for that workload anymore. So the performance improvement is only about 1% for the high_systime workload. Patches 2 and 3 represent different ways to reduce mutex spinning. Of the 2, the third one is better from both a performance perspective and the fact that no mutex data structure change is needed. See the individual patch descriptions for more information on those patches. The table below shows the performance impact on the AIM7 benchmark with a 3.8.5 kernel running on the same 8-socket system mentioned above: +--------------+------------------------------------------------------+ | Workload | Mean % Change 10-100 users | | +-----------------+-----------------+------------------+ | | Patches 1+2 | Patches 1+3 | Relative %Change | +--------------+-----------------+-----------------+------------------+ | fserver | +1.7% | 0.0% | -1.7% | | new_fserver | -0.2% | -1.5% | -1.2% | +--------------+-----------------+-----------------+------------------+ | Workload | Mean % Change 100-1000 users | | +-----------------+-----------------+------------------+ | | Patches 1+2 | Patches 1+3 | Relative %Change | +--------------+-----------------+-----------------+------------------+ | fserver | +18.6% | +43.4% | +21.0% | | new_fserver | +14.0% | +23.4% | +8.2% | +--------------+-----------------+-----------------+------------------+ | Workload | Mean % Change 1100-2000 users | | +-----------------+-----------------+------------------+ | | Patches 1+2 | Patches 1+3 | Relative %Change | +--------------+-----------------+-----------------+------------------+ | fserver | +11.6% | +5.1% | -5.8% | | new_fserver | +13.3% | +7.6% | -5.0% | +--------------+-----------------+-----------------+------------------+ So patch 2 is better at low and high load. Patch 3 is better at intermediate load. For other AIM7 workloads, patch 3 is generally better. Waiman Long (3): mutex: Make more scalable by doing less atomic operations mutex: restrict mutex spinning to only one task per mutex mutex: dynamically disable mutex spinning at high load arch/x86/include/asm/mutex.h | 16 ++++++++++++++++ include/linux/mutex.h | 3 +++ kernel/mutex.c | 21 ++++++++++++++++++--- kernel/mutex.h | 8 ++++++++ kernel/sched/core.c | 22 ++++++++++++++++++++++ 5 files changed, 67 insertions(+), 3 deletions(-) -- 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/
