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.

> 
> d->max_vcpus isn't chosen until a subsequent hypercall.  (This is one of
> many unexpected surprised from multi-vcpu support having been hacked on
> the side of existing Xen support, rather than being built in to the
> createdomain hypercall).
> 
> ~Andrew
> 


-- 
Best regards
Tianyu Lan

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