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SubjectRe: [RFC PATCH 0/3] arm64: queued spinlocks and rw-locks
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On 4/10/2017 5:35 PM, Yury Norov wrote:
> The patch of Jan Glauber enables queued spinlocks on arm64. I rebased it on
> latest kernel sources, and added a couple of fixes to headers to apply it
> smoothly.
>
> Though, locktourture test shows significant performance degradation in the
> acquisition of rw-lock for read on qemu:
>
> Before After
> spin_lock-torture: 38957034 37076367 -4.83
> rw_lock-torture W: 5369471 18971957 253.33
> rw_lock-torture R: 6413179 3668160 -42.80
>

On our 48 core QDF2400 part, I am seeing huge improvements with these patches on
the torture tests. The improvements go up even further when I apply Jason Low's
MCS Spinlock patch: https://lkml.org/lkml/2016/4/20/725

> I'm not much experienced in locking, and so wonder how it's possible that
> simple switching to generic queued rw-lock causes so significant performance
> degradation, while in theory it should improve it. Even more, on x86 there
> are no such problems probably.
>
> I also think that patches 1 and 2 are correct and useful, and should be applied
> anyway.
>
> Any comments appreciated.
>
> Yury.
>

I will be happy to tests these patches more thoroughly after you get some
additional comments/feedback.

> Jan Glauber (1):
> arm64/locking: qspinlocks and qrwlocks support
>
> Yury Norov (2):
> kernel/locking: #include <asm/spinlock.h> in qrwlock.c
> asm-generic: don't #include <linux/atomic.h> in qspinlock_types.h
>
> arch/arm64/Kconfig | 2 ++
> arch/arm64/include/asm/qrwlock.h | 7 +++++++
> arch/arm64/include/asm/qspinlock.h | 20 ++++++++++++++++++++
> arch/arm64/include/asm/spinlock.h | 12 ++++++++++++
> arch/arm64/include/asm/spinlock_types.h | 14 +++++++++++---
> include/asm-generic/qspinlock.h | 1 +
> include/asm-generic/qspinlock_types.h | 8 --------
> kernel/locking/qrwlock.c | 1 +
> 8 files changed, 54 insertions(+), 11 deletions(-)
> create mode 100644 arch/arm64/include/asm/qrwlock.h
> create mode 100644 arch/arm64/include/asm/qspinlock.h
>

Thanks

--
Adam Wallis
Qualcomm Datacenter Technologies as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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