Re: [PATCH v4 0/3] locking/rwsem: Rwsem rearchitecture part 0

Waiman Long
2019-02-15T18:58:34Z

On 02/15/2019 01:40 PM, Will Deacon wrote:
> On Thu, Feb 14, 2019 at 11:37:15AM +0100, Peter Zijlstra wrote:
>> On Wed, Feb 13, 2019 at 05:00:14PM -0500, Waiman Long wrote:
>>> v4:
>>> - Remove rwsem-spinlock.c and make all archs use rwsem-xadd.c.
>>>
>>> v3:
>>> - Optimize __down_read_trylock() for the uncontended case as suggested
>>> by Linus.
>>>
>>> v2:
>>> - Add patch 2 to optimize __down_read_trylock() as suggested by PeterZ.
>>> - Update performance test data in patch 1.
>>>
>>> The goal of this patchset is to remove the architecture specific files
>>> for rwsem-xadd to make it easer to add enhancements in the later rwsem
>>> patches. It also removes the legacy rwsem-spinlock.c file and make all
>>> the architectures use one single implementation of rwsem - rwsem-xadd.c.
>>>
>>> Waiman Long (3):
>>> locking/rwsem: Remove arch specific rwsem files
>>> locking/rwsem: Remove rwsem-spinlock.c & use rwsem-xadd.c for all
>>> archs
>>> locking/rwsem: Optimize down_read_trylock()
>> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>>
>> with the caveat that I'm happy to exchange patch 3 back to my earlier
>> suggestion in case Will expesses concerns wrt the ARM64 performance of
>> Linus' suggestion.
> Right, the current proposal doesn't work well for us, unfortunately. Which
> was your earlier suggestion?
>
> Will

In my posting yesterday, I showed that most of the trylocks done were
actually uncontended. Assuming that pattern hold for the most of the
workloads, it will not that bad after all.

-Longman