Re: [dpdk-dev] [PATCH v1] change hugepage sorting to avoid overlapping memcpy

["Gonzalez Monroy, Sergio" <sergio.gonzalez.monroy@intel.com>]

Hi Ralf,

Just a few comments/suggestions:

Add 'eal/linux:'  to the commit title, ie:
   "eal/linux: change hugepage sorting to avoid overlapping memcpy"

On 04/09/2015 11:14, Ralf Hoffmann wrote:
> with only one hugepage or already sorted hugepage addresses, the sort
> function called memcpy with same src and dst pointer. Debugging with
> valgrind will issue a warning about overlapping area. This patch changes
> the bubble sort to avoid this behavior. Also, the function cannot fail
> any longer.
>
> Signed-off-by: Ralf Hoffmann <ralf.hoffmann@allegro-packets.com>
> ---
>   lib/librte_eal/linuxapp/eal/eal_memory.c | 27 +++++++++++++--------------
>   1 file changed, 13 insertions(+), 14 deletions(-)
>
> diff --git a/lib/librte_eal/linuxapp/eal/eal_memory.c b/lib/librte_eal/linuxapp/eal/eal_memory.c
> index ac2745e..6d01f61 100644
> --- a/lib/librte_eal/linuxapp/eal/eal_memory.c
> +++ b/lib/librte_eal/linuxapp/eal/eal_memory.c
> @@ -699,25 +699,25 @@ error:
>    * higher address first on powerpc). We use a slow algorithm, but we won't
>    * have millions of pages, and this is only done at init time.
>    */
> -static int
> +static void
>   sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi)
>   {
>   	unsigned i, j;
> -	int compare_idx;
> +	unsigned compare_idx;
>   	uint64_t compare_addr;
>   	struct hugepage_file tmp;
>   
>   	for (i = 0; i < hpi->num_pages[0]; i++) {
> -		compare_addr = 0;
> -		compare_idx = -1;
> +		compare_addr = hugepg_tbl[i].physaddr;
> +		compare_idx = i;
>   
>   		/*
> -		 * browse all entries starting at 'i', and find the
> +		 * browse all entries starting at 'i+1', and find the
>   		 * entry with the smallest addr
>   		 */
> -		for (j=i; j< hpi->num_pages[0]; j++) {
> +		for (j=i + 1; j < hpi->num_pages[0]; j++) {
Although there are many style/checkpatch issues in current code, we try 
to fix them
in new patches.
In that regard, checkpatch complains about above line with:
ERROR:SPACING: spaces required around that '='

>   
> -			if (compare_addr == 0 ||
> +			if (
>   #ifdef RTE_ARCH_PPC_64
>   				hugepg_tbl[j].physaddr > compare_addr) {
>   #else
> @@ -728,10 +728,9 @@ sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi)
>   			}
>   		}
>   
> -		/* should not happen */
> -		if (compare_idx == -1) {
> -			RTE_LOG(ERR, EAL, "%s(): error in physaddr sorting\n", __func__);
> -			return -1;
> +		if (compare_idx == i) {
> +			/* no smaller page found */
> +			continue;
>   		}
>   
>   		/* swap the 2 entries in the table */
> @@ -741,7 +740,8 @@ sort_by_physaddr(struct hugepage_file *hugepg_tbl, struct hugepage_info *hpi)
>   			sizeof(struct hugepage_file));
>   		memcpy(&hugepg_tbl[i], &tmp, sizeof(struct hugepage_file));
>   	}
> -	return 0;
> +
> +	return;
>   }
I reckon checkpatch is not picking this one because the end-of-function 
is not part of the patch,
but it is a warning:
WARNING:RETURN_VOID: void function return statements are not generally 
useful

>   
>   /*
> @@ -1164,8 +1164,7 @@ rte_eal_hugepage_init(void)
>   			goto fail;
>   		}
>   
> -		if (sort_by_physaddr(&tmp_hp[hp_offset], hpi) < 0)
> -			goto fail;
> +		sort_by_physaddr(&tmp_hp[hp_offset], hpi);
>   
>   #ifdef RTE_EAL_SINGLE_FILE_SEGMENTS
>   		/* remap all hugepages into single file segments */
>
>

Thanks,
Sergio