Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16

From	Waiman Long <waiman.long@hpe.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16
Date	2016-04-13 18:00 +0200
Message-ID	<rnvmW-3u7-23@gated-at.bofh.it> (permalink)
References	<rlyoW-8fi-9@gated-at.bofh.it> <rlzl0-rS-13@gated-at.bofh.it> <rmonw-6i9-9@gated-at.bofh.it> <rn7DY-p6-23@gated-at.bofh.it> <rnqZY-n3-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

Show all headers | View raw

On 04/13/2016 07:15 AM, Pan Xinhui wrote:
> Hello Peter,
>
> On 2016年04月12日 22:30, Peter Zijlstra wrote:
>
>>> I am working on the qspinlock implementation on PPC.
>>> Your and Waiman's patches are so nice. :)
>> Thanks!, last time I looked at PPC spinlocks they could not use things
>> like ticket locks because PPC might be a guest and fairness blows etc..
>>
>> You're making the qspinlock-paravirt thing work on PPC, or doing
>> qspinlock only for bare-metal PPC?
>>
> I am making the both work. :)
> qspinlock works on PPC now. I am preparing the patches and will send them out in next weeks :)

What of performance improvement are you seeing in PPC?

> The paravirt work is a little hard.
> currently, there are pv_wait() and pv_kick(). but only pv_kick has the parameter cpu(who will hold the lock as soon as the lock is unlocked).
> We need parameter cpu(who holds the lock now) in pv_wait,too.

That can be doable to a certain extent. However, if the current lock 
holder acquired the lock via the fastpath only. The CPU information is 
not logged anywhere. For a contended lock, the information should be there.

Cheers,
Longman

Thread

[PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-04-08 08:50 +0200
  Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Peter Zijlstra <peterz@infradead.org> - 2016-04-08 09:50 +0200
    Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-04-10 16:20 +0200
      Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Peter Zijlstra <peterz@infradead.org> - 2016-04-12 16:40 +0200
        Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-04-13 13:20 +0200
          Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Waiman Long <waiman.long@hpe.com> - 2016-04-13 18:00 +0200
            Re: [PATCH] powerpc: introduce {cmp}xchg for u8 and u16 Pan Xinhui <xinhui@linux.vnet.ibm.com> - 2016-04-14 10:40 +0200

csiph-web