On Thu, Feb 14, 2019 at 10:09:44AM -0800, Linus Torvalds wrote:
> On Thu, Feb 14, 2019 at 9:51 AM Linus Torvalds
> wrote:
> >
> > The arm64 numbers scaled horribly even before, and that's because
> > there is too much ping-pong, and it's probably because there is no
> > "stickiness" to the
On 02/14/2019 01:02 PM, Will Deacon wrote:
> On Thu, Feb 14, 2019 at 11:33:33AM +0100, Peter Zijlstra wrote:
>> On Wed, Feb 13, 2019 at 03:32:12PM -0500, Waiman Long wrote:
>>> Modify __down_read_trylock() to optimize for an unlocked rwsem and make
>>> it generate slightly better code.
>>>
>>>
On Thu, Feb 14, 2019 at 9:51 AM Linus Torvalds
wrote:
>
> The arm64 numbers scaled horribly even before, and that's because
> there is too much ping-pong, and it's probably because there is no
> "stickiness" to the cacheline to the core, and thus adding the extra
> loop can make the ping-pong
On Thu, Feb 14, 2019 at 11:33:33AM +0100, Peter Zijlstra wrote:
> On Wed, Feb 13, 2019 at 03:32:12PM -0500, Waiman Long wrote:
> > Modify __down_read_trylock() to optimize for an unlocked rwsem and make
> > it generate slightly better code.
> >
> > Before this patch, down_read_trylock:
> >
> >
On Thu, Feb 14, 2019 at 6:53 AM Waiman Long wrote:
>
> The ARM64 result is what I would have expected given that the change was
> to optimize for the uncontended case. The x86-64 result is kind of an
> anomaly to me, but I haven't bothered to dig into that.
I would say that the ARM result is
On 02/14/2019 05:33 AM, Peter Zijlstra wrote:
> On Wed, Feb 13, 2019 at 03:32:12PM -0500, Waiman Long wrote:
>> Modify __down_read_trylock() to optimize for an unlocked rwsem and make
>> it generate slightly better code.
>>
>> Before this patch, down_read_trylock:
>>
>>0x <+0>:
On Wed, Feb 13, 2019 at 03:32:12PM -0500, Waiman Long wrote:
> Modify __down_read_trylock() to optimize for an unlocked rwsem and make
> it generate slightly better code.
>
> Before this patch, down_read_trylock:
>
>0x <+0>: callq 0x5
>0x0005 <+5>:
