Re: [PATCH 2/2] xen/heap: pass order to free_heap_pages() in heap init

[Julien Grall <julien@xen.org>]

On 28/06/2022 15:40, Bertrand Marquis wrote:
> Hi Julien,

Hi Bertrand,

>> On 9 Jun 2022, at 09:30, Julien Grall <julien@xen.org> wrote:
>>
>> From: Hongyan Xia <hongyxia@amazon.com>
>>
>> The idea is to split the range into multiple aligned power-of-2 regions
>> which only needs to call free_heap_pages() once each. We check the least
>> significant set bit of the start address and use its bit index as the
>> order of this increment. This makes sure that each increment is both
>> power-of-2 and properly aligned, which can be safely passed to
>> free_heap_pages(). Of course, the order also needs to be sanity checked
>> against the upper bound and MAX_ORDER.
>>
>> Testing on a nested environment on c5.metal with various amount
>> of RAM. Time for end_boot_allocator() to complete:
>>             Before         After
>>     - 90GB: 1426 ms        166 ms
>>     -  8GB:  124 ms         12 ms
>>     -  4GB:   60 ms          6 ms
> 
> 
> On a arm64 Neoverse N1 system with 32GB of Ram I have:
> - 1180 ms before
> - 63 ms after
> 
> and my internal tests are passing on arm64.

Thanks for the testing! The number are a lot better than I was actually 
expecting on arm64.

> 
> Great optimisation :-)

You will have to thanks Hongyan. He came up with the idea :).

> 
> (I will do a full review of code the in a second step).

I am planning to send a new version in the next few days. So you may 
want to wait before reviewing the series.

Cheers,

-- 
Julien Grall