[dpdk-dev] [PATCH] mem: unmap unneeded space

[Bruce Richardson]

On Thu, Apr 19, 2018 at 05:35:25PM +0100, Anatoly Burakov wrote:
> When we ask to reserve virtual areas, we usually include
> alignment in the mapping size, and that memory ends up
> being wasted. Wasting a gigabyte of VA space while trying to
> reserve one gigabyte is pretty expensive on 32-bit, so after
> we're done mapping, unmap unneeded space.
> 
> Signed-off-by: Anatoly Burakov <anatoly.burakov at intel.com>
> ---
>  lib/librte_eal/common/eal_common_memory.c | 23 +++++++++++++++++++++--
>  1 file changed, 21 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/librte_eal/common/eal_common_memory.c b/lib/librte_eal/common/eal_common_memory.c
> index 24a9ed5..8dd026a 100644
> --- a/lib/librte_eal/common/eal_common_memory.c
> +++ b/lib/librte_eal/common/eal_common_memory.c
> @@ -75,8 +75,13 @@ eal_get_virtual_area(void *requested_addr, size_t *size,
>  
>  	do {
>  		map_sz = no_align ? *size : *size + page_sz;
> +		if (map_sz > SIZE_MAX) {
> +			RTE_LOG(ERR, EAL, "Map size too big\n");
> +			rte_errno = E2BIG;
> +			return NULL;
> +		}
>  
> -		mapped_addr = mmap(requested_addr, map_sz, PROT_READ,
> +		mapped_addr = mmap(requested_addr, (size_t)map_sz, PROT_READ,
>  				mmap_flags, -1, 0);
>  		if (mapped_addr == MAP_FAILED && allow_shrink)
>  			*size -= page_sz;

This part looks like it should be a separate patch, since it's not related
to unmapping.

/Bruce