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Re: [PATCH 2/2] xen/arm: Skip loops in init_pdx() when no PDX compression is used


  • To: Julien Grall <julien@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
  • From: "Orzel, Michal" <michal.orzel@xxxxxxx>
  • Date: Mon, 14 Jul 2025 11:50:43 +0200
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Bertrand Marquis <bertrand.marquis@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>
  • Delivery-date: Mon, 14 Jul 2025 09:51:01 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>


On 14/07/2025 11:45, Julien Grall wrote:
> Hi Michal,
> 
> On 14/07/2025 08:37, Orzel, Michal wrote:
>>
>>
>> On 12/07/2025 12:29, Julien Grall wrote:
>>> Hi Michal,
>>>
>>> On 04/07/2025 08:54, Michal Orzel wrote:
>>>> When CONFIG_PDX_COMPRESSION=n, pdx_init_mask(), pdx_region_mask() and
>>>> pfn_pdx_hole_setup() are just stubs doing nothing. It does not make
>>>> sense to keep the two loops iterating over all the memory banks.
>>>
>>> I saw this was already committed. But I have a question. Wouldn't the
>>> compiler be able to optimize and remove the loops? Asking because we are
>>> trying to limit the number of #ifdef in the code hence why we have stubs.
>> Before submitting a patch I did disassembled init_pdx() with and without my
>> patch and in the latter case the compiler did not optimize out the loops.
> 
> One more question. Was this in debug or non-debug build?
It was in debug build.

~Michal




 


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