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RE: [Xen-devel] Re: Will map_domain_page return NULL when fails onx86_32?

  • To: "Keir Fraser" <Keir.Fraser@xxxxxxxxxxxx>
  • From: "Li, Xin B" <xin.b.li@xxxxxxxxx>
  • Date: Mon, 27 Feb 2006 22:13:24 +0800
  • Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Mon, 27 Feb 2006 14:13:58 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcY7pIIrROwekCuORH26HDX9YQn0NQAAD36w
  • Thread-topic: [Xen-devel] Re: Will map_domain_page return NULL when fails onx86_32?

>>>> Hi Keir, just a curious question, will map_domain_page
>>> return NULL when
>>>> fails on x86_32? If not, why?
>>>> thanks
>>> I don't expect that it should ever fail. It's used for temporary
>>> mappings (e.g., scope of a function) and so even though the mapping
>>> space is finite, we shouldn't ever exhaust it.
>> So the unmap is not a must?
>> Can you explain the mechanism of garbage collection here?
>> Thanks
>The unmap is a must. After unmap the mapping is put in a per-vcpu 
>lookup table to allow fast reuse. When it is evicted from that table 
>then it is freed.

Quite clear, thanks, this may be helpful to accelerate __entry().

>  -- Keir
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