linux-kernel - [PATCH 0/2] locking/mutex: Enable optimistic spinning of lock waiter

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite for Android: free password hash cracker in your pocket

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-Id: <1455047262-27731-1-git-send-email-Waiman.Long@hpe.com>
Date:	Tue,  9 Feb 2016 14:47:40 -0500
From:	Waiman Long <Waiman.Long@....com>
To:	Ingo Molnar <mingo@...hat.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ding Tianhong <dingtianhong@...wei.com>,
	Jason Low <jason.low2@....com>,
	Davidlohr Bueso <dave@...olabs.net>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <Will.Deacon@....com>,
	Tim Chen <tim.c.chen@...ux.intel.com>,
	Waiman Long <Waiman.Long@....com>
Subject: [PATCH 0/2] locking/mutex: Enable optimistic spinning of lock waiter

This patchset is a variant of PeterZ's "locking/mutex: Avoid spinner
vs waiter starvation" patch. The major difference is that the
waiter-spinner won't enter into the OSQ used by the spinners. Instead,
it will spin directly on the lock in parallel with the queue head
of the OSQ. So there will be a bit more cacheline contention on the
lock cacheline, but that shouldn't cause noticeable impact on system
performance.

This patchset tries to address 2 issues with Peter's patch:

 1) Ding Tianhong still find that hanging task could happen in some cases.
 2) Jason Low found that there was performance regression for some AIM7
    workloads.

By making the waiter-spinner to spin directly on the mutex, it will
increase the chance for the waiter-spinner to get the lock instead
of waiting in the OSQ for its turn.

My own test on a 4-socket E7-4820 v3 system showed a regression of
about 4% in the high_systime workload with Peter's patch which this
new patch effectively eliminates.

Waiman Long (2):
  locking/mutex: Add waiter parameter to mutex_optimistic_spin()
  locking/mutex: Enable optimistic spinning of woken task in wait queue

 kernel/locking/mutex.c |   68 ++++++++++++++++++++++++++++++++++-------------
 1 files changed, 49 insertions(+), 19 deletions(-)