linux-kernel - Re: [PATCH] xen: add steal

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Message-ID: <573C81D1.9040309@suse.com>
Date:	Wed, 18 May 2016 16:53:05 +0200
From:	Juergen Gross <jgross@...e.com>
To:	Boris Ostrovsky <boris.ostrovsky@...cle.com>,
	xen-devel@...ts.xenproject.org, linux-kernel@...r.kernel.org
Cc:	sstabellini@...nel.org, david.vrabel@...rix.com
Subject: Re: [PATCH] xen: add steal_clock support on x86

On 18/05/16 16:46, Boris Ostrovsky wrote:
> On 05/18/2016 08:15 AM, Juergen Gross wrote:
>>  }
>>  
>> +void __init xen_time_setup_guest(void)
>> +{
>> +	pv_time_ops.steal_clock = xen_steal_clock;
>> +
>> +	static_key_slow_inc(&paravirt_steal_enabled);
>> +	/*
>> +	 * We can't set paravirt_steal_rq_enabled as this would require the
>> +	 * capability to read another cpu's runstate info.
>> +	 */
>> +}
> 
> Won't we be accounting for stolen cycles twice now --- once from
> steal_account_process_tick()->steal_clock() and second time from
> do_stolen_accounting()?

Uuh, yes.

I guess I should rip do_stolen_accounting() out, too? It is a
Xen-specific hack, so I guess nobody will cry. Maybe it would be a
good idea to select CONFIG_PARAVIRT_TIME_ACCOUNTING for XEN then?


Juergen