[dpdk-stable] [dpdk-dev] [PATCH 17.11] mem: fix memory initialization time

[Burakov, Anatoly]

On 12-Nov-18 11:18 AM, Alejandro Lucero wrote:
> When using large amount of hugepage based memory, doing all the
> hugepages mapping can take quite significant time.
> 
> The problem is hugepages being initially mmaped to virtual addresses
> which will be tried later for the final hugepage mmaping. This causes
> the final mapping requiring calling mmap with another hint address which
> can happen several times, depending on the amount of memory to mmap, and
> which each mmmap taking more than a second.
> 
> This patch changes the hint for the initial hugepage mmaping using
> a starting address which will not collide with the final mmaping.
> 
> Fixes: 293c0c4b957f ("mem: use address hint for mapping hugepages")
> 
> Signed-off-by: Alejandro Lucero <alejandro.lucero at netronome.com>
> ---

Hi Alejandro,

I'm not sure i understand the purpose. When final mapping is performed, 
we reserve new memory area, and map pages into it. (i don't quite 
understand why we unmap the area before mapping pages, but it's how it's 
always been and i didn't change it in the legacy code)

Which addresses are causing the collision?

-- 
Thanks,
Anatoly