From: xinhui <xinhui.pan@linux.vnet.ibm.com>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
virtualization@lists.linux-foundation.org
Cc: paulus@samba.org, mpe@ellerman.id.au, peterz@infradead.org,
mingo@redhat.com, paulmck@linux.vnet.ibm.com,
waiman.long@hpe.com
Subject: Re: [PATCH v5 1/6] qspinlock: powerpc support qspinlock
Date: Fri, 03 Jun 2016 15:02:11 +0800 [thread overview]
Message-ID: <57512B73.5010005@linux.vnet.ibm.com> (raw)
In-Reply-To: <1464928427.26773.26.camel@kernel.crashing.org>
On 2016年06月03日 12:33, Benjamin Herrenschmidt wrote:
> On Fri, 2016-06-03 at 12:10 +0800, xinhui wrote:
>> On 2016年06月03日 09:32, Benjamin Herrenschmidt wrote:
>>> On Fri, 2016-06-03 at 11:32 +1000, Benjamin Herrenschmidt wrote:
>>>> On Thu, 2016-06-02 at 17:22 +0800, Pan Xinhui wrote:
>>>>>
>>>>> Base code to enable qspinlock on powerpc. this patch add some
>>>>> #ifdef
>>>>> here and there. Although there is no paravirt related code, we
>> can
>>>>> successfully build a qspinlock kernel after apply this patch.
>>>> This is missing the IO_SYNC stuff ... It means we'll fail to do a
>>>> full
>>>> sync to order vs MMIOs.
>>>>
>>>> You need to add that back in the unlock path.
>>>
>>> Well, and in the lock path as well...
>>>
>> Oh, yes. I missed IO_SYNC stuff.
>>
>> thank you, Ben :)
>
> Ok couple of other things that would be nice from my perspective (and
> Michael's) if you can produce them:
>
> - Some benchmarks of the qspinlock alone, without the PV stuff,
> so we understand how much of the overhead is inherent to the
> qspinlock and how much is introduced by the PV bits.
>
> - For the above, can you show (or describe) where the qspinlock
> improves things compared to our current locks. While there's
> theory and to some extent practice on x86, it would be nice to
> validate the effects on POWER.
>
> - Comparative benchmark with the PV stuff in on a bare metal system
> to understand the overhead there.
>
> - Comparative benchmark with the PV stuff under pHyp and KVM
>
Will do such benchmark tests in next days.
thanks for your kind suggestions. :)
> Spinlocks are fiddly and a critical piece of infrastructure, it's
> important we fully understand the performance implications before we
> decide to switch to a new model.
>
yes, We really need understand how {pv}qspinlock works in more complex cases.
thanks
xinhui
> Cheers,
> Ben.
>
next prev parent reply other threads:[~2016-06-03 7:03 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <1464859370-5162-1-git-send-email-xinhui.pan@linux.vnet.ibm.com>
[not found] ` <1464859370-5162-3-git-send-email-xinhui.pan@linux.vnet.ibm.com>
[not found] ` <1464917520.26773.11.camel@kernel.crashing.org>
[not found] ` <1464917548.26773.12.camel@au1.ibm.com>
2016-06-03 4:10 ` [PATCH v5 1/6] qspinlock: powerpc support qspinlock xinhui
2016-06-03 4:33 ` Benjamin Herrenschmidt
2016-06-03 7:02 ` xinhui [this message]
2016-06-06 15:59 ` Peter Zijlstra
2016-06-06 21:41 ` Benjamin Herrenschmidt
2016-06-21 12:35 ` xinhui
2016-06-02 9:26 [PATCH v5 0/6] powerPC/pSeries use pv-qpsinlock as the default spinlock implemention Pan Xinhui
2016-06-02 9:26 ` [PATCH v5 1/6] qspinlock: powerpc support qspinlock Pan Xinhui
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