linux-kernel - Re: [PATCH 0/6] x86: reduce paravirtualized spinlock overhead

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Message-ID: <558034B1.1030906@suse.com>
Date:	Tue, 16 Jun 2015 16:37:37 +0200
From:	Juergen Gross <jgross@...e.com>
To:	linux-kernel@...r.kernel.org, x86@...nel.org, hpa@...or.com,
	tglx@...utronix.de, mingo@...hat.com,
	xen-devel@...ts.xensource.com, konrad.wilk@...cle.com,
	david.vrabel@...rix.com, boris.ostrovsky@...cle.com,
	jeremy@...p.org, chrisw@...s-sol.org, akataria@...are.com,
	rusty@...tcorp.com.au, virtualization@...ts.linux-foundation.org,
	gleb@...nel.org, pbonzini@...hat.com, kvm@...r.kernel.org
Subject: Re: [PATCH 0/6] x86: reduce paravirtualized spinlock overhead

AFAIK there are no outstanding questions for more than one month now.
I'd appreciate some feedback or accepting these patches.


Juergen

On 04/30/2015 12:53 PM, Juergen Gross wrote:
> Paravirtualized spinlocks produce some overhead even if the kernel is
> running on bare metal. The main reason are the more complex locking
> and unlocking functions. Especially unlocking is no longer just one
> instruction but so complex that it is no longer inlined.
>
> This patch series addresses this issue by adding two more pvops
> functions to reduce the size of the inlined spinlock functions. When
> running on bare metal unlocking is again basically one instruction.
>
> Compile tested with CONFIG_PARAVIRT_SPINLOCKS on and off, 32 and 64
> bits.
>
> Functional testing on bare metal and as Xen dom0.
>
> Correct patching verified by disassembly of active kernel.
>
> Juergen Gross (6):
>    x86: use macro instead of "0" for setting TICKET_SLOWPATH_FLAG
>    x86: move decision about clearing slowpath flag into arch_spin_lock()
>    x86: introduce new pvops function clear_slowpath
>    x86: introduce new pvops function spin_unlock
>    x86: switch config from UNINLINE_SPIN_UNLOCK to INLINE_SPIN_UNLOCK
>    x86: remove no longer needed paravirt_ticketlocks_enabled
>
>   arch/x86/Kconfig                      |  1 -
>   arch/x86/include/asm/paravirt.h       | 13 +++++++++
>   arch/x86/include/asm/paravirt_types.h | 12 ++++++++
>   arch/x86/include/asm/spinlock.h       | 53 ++++++++++++-----------------------
>   arch/x86/include/asm/spinlock_types.h |  3 +-
>   arch/x86/kernel/kvm.c                 | 14 +--------
>   arch/x86/kernel/paravirt-spinlocks.c  | 42 +++++++++++++++++++++++++--
>   arch/x86/kernel/paravirt.c            | 12 ++++++++
>   arch/x86/kernel/paravirt_patch_32.c   | 25 +++++++++++++++++
>   arch/x86/kernel/paravirt_patch_64.c   | 24 ++++++++++++++++
>   arch/x86/xen/spinlock.c               | 23 +--------------
>   include/linux/spinlock_api_smp.h      |  2 +-
>   kernel/Kconfig.locks                  |  7 +++--
>   kernel/Kconfig.preempt                |  3 +-
>   kernel/locking/spinlock.c             |  2 +-
>   lib/Kconfig.debug                     |  1 -
>   16 files changed, 154 insertions(+), 83 deletions(-)
>

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