linux-kernel - Re: [GIT PULL] Locking changes for v4.2

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Date:	Fri, 26 Jun 2015 11:11:50 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Paul E. McKenney" <paulmck@...ibm.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] Locking changes for v4.2

On Mon, 2015-06-22 at 09:30 +0200, Ingo Molnar wrote:
> Linus,
> 
> Please pull the latest locking-core-for-linus git tree from:
> 
>    git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git locking-core-for-linus
> 
>    # HEAD: 68722101ec3a0e179408a13708dd020e04f54aab locking/lockdep: Remove hard coded array size dependency
> 
> The main changes are:
> 
>  - 'qspinlock' support, enabled on x86: queued spinlocks - these are now the 
>    spinlock variant used by x86 as they outperform ticket spinlocks in every 
>    category. (Waiman Long)

Very interesting.

While rebasing http://www.kernelhub.org/?msg=737214&p=2

I found that indeed qspinlock improved the scalability issue by a big
factor.

linux-4.1

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 6977349, ops/sec 232578
6977349

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 7326280, ops/sec 244209
7326280


Current Linus tree :

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 15640802, ops/sec 521360
15640802

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 15045022, ops/sec 501500
15045022


Adding fd_install() patch then :

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 21471043, ops/sec 715701
21471043

lpaa23:~# pipebench -n 16
threads:16 sleep:30 pinned:1
total operations: 21068501, ops/sec 702283
21068501





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