Re: [Xen-devel] [PATCH] x86/PoD: skip eager reclaim when possible

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 12.05.16 at 16:40, <george.dunlap@xxxxxxxxxx> wrote:
> On 10/05/16 14:44, Jan Beulich wrote:
>> Reclaiming pages is pointless when the cache can already satisfy all
>> outstanding PoD entries, and doing reclaims in that case can be very
>> harmful to performance when that memory gets used by the guest, but
>> only to store zeroes there.
>> 
>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
> 
> Sorry for the delay.  Just one question...
> 
>> 
>> --- a/xen/arch/x86/mm/p2m-pod.c
>> +++ b/xen/arch/x86/mm/p2m-pod.c
>> @@ -1027,7 +1027,6 @@ static void pod_eager_record(struct p2m_
>>  {
>>      struct pod_mrp_list *mrp = &p2m->pod.mrp;
>>  
>> -    ASSERT(mrp->list[mrp->idx] == INVALID_GFN);
>>      ASSERT(gfn != INVALID_GFN);
> 
> What's this for?

The deletion of the ASSERT()? Since we no longer always insert a
GFN through pod_eager_reclaim(), we also can no longer assume
all (used) entries hold a valid GFN.

Jan


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