linux-kernel - [PATCH 0/3] timer: Improve itimers scalability

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Message-Id: <1440559068-29680-1-git-send-email-jason.low2@hp.com>
Date:	Tue, 25 Aug 2015 20:17:45 -0700
From:	Jason Low <jason.low2@...com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Oleg Nesterov <oleg@...hat.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org,
	Frederic Weisbecker <fweisbec@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Davidlohr Bueso <dave@...olabs.net>,
	Steven Rostedt <rostedt@...dmis.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Terry Rudd <terry.rudd@...com>, Rik van Riel <riel@...hat.com>,
	Scott J Norton <scott.norton@...com>,
	Jason Low <jason.low2@...com>
Subject: [PATCH 0/3] timer: Improve itimers scalability

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(-)

-- 
1.7.2.5

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