Re: [Xen-devel] [RFC PATCH V2 1/4] xen/hap: Increase hap page pool size for more vcpus support

[Lan Tianyu <tianyu.lan@xxxxxxxxx>]

On 2017年09月01日 16:34, Jan Beulich wrote:
>>>> On 01.09.17 at 10:19, <tianyu.lan@xxxxxxxxx> wrote:
>> On 2017年08月31日 21:56, Andrew Cooper wrote:
>>> On 31/08/17 06:01, Lan Tianyu wrote:
>>>> This patch is to increase hap page pool size to support more vcpus in 
>>>> single 
>> VM.
>>>>
>>>> Signed-off-by: Lan Tianyu <tianyu.lan@xxxxxxxxx>
>>>> ---
>>>>  xen/arch/x86/mm/hap/hap.c | 10 +++++++++-
>>>>  1 file changed, 9 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
>>>> index cdc77a9..96a7ed0 100644
>>>> --- a/xen/arch/x86/mm/hap/hap.c
>>>> +++ b/xen/arch/x86/mm/hap/hap.c
>>>> @@ -464,6 +464,7 @@ void hap_domain_init(struct domain *d)
>>>>  int hap_enable(struct domain *d, u32 mode)
>>>>  {
>>>>      unsigned int old_pages;
>>>> +    unsigned int pages;
>>>>      unsigned int i;
>>>>      int rv = 0;
>>>>  
>>>> @@ -473,7 +474,14 @@ int hap_enable(struct domain *d, u32 mode)
>>>>      if ( old_pages == 0 )
>>>>      {
>>>>          paging_lock(d);
>>>> -        rv = hap_set_allocation(d, 256, NULL);
>>>> +
>>>> +        /* Increase hap page pool with max vcpu number. */
>>>> +        if ( d->max_vcpus > 128 )
>>>> +            pages = 256;
>>>> +        else
>>>> +            pages = 512;
>>>> +
>>>> +        rv = hap_set_allocation(d, pages, NULL);
>>>
>>> What effect is this intended to have?  hap_enable() is always called
>>> when d->max_vcpus is 0.
>>
>> Sorry. I didn't notice that max_vcpus wasn't set at that point.I hope to
>> allocate hap pages according vcpu number. This means we don't know how
>> many vcpu will be used when allocate hap pages during creating domain,
>> right? If that, we have to increase page number unconditionally.
> 
> But that you were already told isn't really acceptable. Did you
> consider calling hap_set_allocation() another time once vCPU
> count was set?
> 

That sounds feasible. I will try it. Thanks.


-- 
Best regards
Tianyu Lan

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