While running a database workload on a 16 socket machine, there were scalability issues related to itimers. The following link contains a more detailed summary of the issues at the application level.
https://lkml.org/lkml/2015/8/26/737 Commit 1018016c706f addressed the issue with the thread_group_cputimer spinlock taking up a significant portion of total run time. This patch series addresses the secondary issue where a lot of time is spent trying to acquire the sighand lock. It was found in some cases that 200+ threads were simultaneously contending for the same sighand lock, reducing throughput by more than 30%. With this patch set (along with commit 1018016c706f mentioned above), the performance hit of itimers almost completely goes away on the 16 socket system. Jason Low (4): timer: Optimize fastpath_timer_check() timer: Check thread timers only when there are active thread timers timer: Convert cputimer->running to bool timer: Reduce unnecessary sighand lock contention include/linux/init_task.h | 3 +- include/linux/sched.h | 9 ++++-- kernel/fork.c | 2 +- kernel/time/posix-cpu-timers.c | 63 ++++++++++++++++++++++++++++----------- 4 files changed, 54 insertions(+), 23 deletions(-) -- 1.7.2.5 -- 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/
