Re: [PATCH v2 2/5] mem: use address hint for mapping hugepages

["Burakov, Anatoly" <anatoly.burakov@intel.com>]

On 31-Aug-18 1:50 PM, Alejandro Lucero wrote:
> Linux kernel uses a really high address as starting address for
> serving mmaps calls. If there exist addressing limitations and
> IOVA mode is VA, this starting address is likely too high for
> those devices. However, it is possible to use a lower address in
> the process virtual address space as with 64 bits there is a lot
> of available space.
> 
> This patch adds an address hint as starting address for 64 bits
> systems.
> 
> Signed-off-by: Alejandro Lucero <alejandro.lucero@netronome.com>
> ---

<snip>

>   
>   		mapped_addr = mmap(requested_addr, (size_t)map_sz, PROT_READ,
>   				mmap_flags, -1, 0);
> +
>   		if (mapped_addr == MAP_FAILED && allow_shrink)

Unintended whitespace change?

>   			*size -= page_sz;
> -	} while (allow_shrink && mapped_addr == MAP_FAILED && *size > 0);
> +
> +		if (mapped_addr != MAP_FAILED && addr_is_hint &&
> +		    mapped_addr != requested_addr) {
> +			/* hint was not used. Try with another offset */
> +			munmap(mapped_addr, map_sz);
> +			mapped_addr = MAP_FAILED;
> +			next_baseaddr = RTE_PTR_ADD(next_baseaddr, 0x100000000);

Why not increment by page size? Sure, it could take some more time to 
allocate, but will result in less wasted memory.

-- 
Thanks,
Anatoly