[PATCH 0/3] timer: Improve itimers scalability

[Jason Low <jason.low2@hp.com>]

When running a database workload on a 16 socket machine, there were
scalability issues related to itimers.

Commit 1018016c706f addressed the issue with the thread_group_cputimer
spinlock taking up a significant portion of total run time.

This patch series address the other 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%.

Jason Low (3):
  timer: Optimize fastpath_timer_check()
  timer: Check thread timers only when there are active thread timers
  timer: Reduce unnecessary sighand lock contention

 include/linux/init_task.h      |    1 +
 include/linux/sched.h          |    3 ++
 kernel/time/posix-cpu-timers.c |   44 +++++++++++++++++++++++++++------------
 3 files changed, 34 insertions(+), 14 deletions(-)

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1.7.2.5