Re: [Xen-devel] [PATCH for 4.7] xen: Replace alloc_vcpu_guest_context() with vmalloc()

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 21.08.15 at 20:10, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 21/08/15 18:55, Konrad Rzeszutek Wilk wrote:
>> On Fri, Aug 21, 2015 at 06:51:46PM +0100, Andrew Cooper wrote:
>>> This essentially reverts c/s 2037f2adb "x86: introduce
>>> alloc_vcpu_guest_context()", including the newer arm bits, but achieves
>>> the same end goal by using the newer vmalloc() infrastructure.
>> Could you explain what this fixes? Or perhaps with an explanation
>> of why this will make Xen [ ]better; [ ] faster [ ] magical.
>>
>> :-)
> 
> Ain't the diffstat enough to qualify for [x]better ;) ?
> 
>>
>>
>> Thanks.
> 
> It is relevant to a patch of Rogers which I am reviewing from the no-DM
> series.  I was writing in reply to that, but this can also do.
> 
> alloc_vcpu_guest_context() was introduced long before vmalloc(), and
> attempts to make the same end result using per-pcpu fixmap entries,
> which scale by the compile-time NR_CPUS.
> 
> This patch causes a net reduction in compiled size for each arch (small
> for ARM, larger for x86) and removes a scalability limit for compiling
> with large numbers of cpus.
> 
> I think I can guess what you are going to ask me to do, given this
> explanation.

To be honest the patch (and its description) looks fine to me as is.

Jan


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