Re: [Xen-devel] Linux v3.12 + pv ticketlocks

[Sander Eikelenboom <linux@xxxxxxxxxxxxxx>]

Wednesday, September 11, 2013, 8:41:29 PM, you wrote:

> On Wed, Sep 11, 2013 at 08:25:01PM +0200, Sander Eikelenboom wrote:
>> Hi Konrad,
>> 
>> Just to confirm:
>> 
>> - PV ticketlocks is on by default and doesn't neet a config option, to 
>> disable it at boot time it's  possible to use "xen_nopvspin" as a kernel 
>> commandline parameter

> Yes.
>> - CONFIG_PARAVIRT_SPINLOCKS should be off, since that would enable the old 
>> bytelock pv-spinlock implementation which could now probably be removed ?

> You still need CONFIG_PARAVIRT_SPINLOCKS=y to take advantage of it.

> The bytelock pvspinlock is gone. If you compile without 
> CONFIG_PARAVIRT_SPINLOCKS
> then you will only use ticketlocks for all types of guests and baremtal. No
> 'PV' variant.

> The CONFIG_PARAVIRT_SPINLOCKS=y enables the PV ticketlock for all guests.

Ok so the KConfig (help) entry for CONFIG_PARAVIRT_SPINLOCKS should perhaps 
also be updated ?

Since it for example still contains the "Unfortunately the downside is an up to 
5%
performance hit on native kernels, with various workloads." which afaik was one 
the things the PV ticketlock migitated,
so it would be more feasible for distributions to have this option on for all 
general distro kernels ?

--
Sander




>> 
>> Have a nice vacation !
>> 
>> --
>> Sander
>> 



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