Re: [dpdk-dev] [PATCH] net/virtio-user: fix hugepage files enumeration

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

On 26-Apr-18 4:34 PM, Jianfeng Tan wrote:
> After the commit 2a04139f66b4 ("eal: add single file segments option"),
> one hugepage file could contain multiple hugepages which are further
> mapped to different memory regions.
> 
> Original enumeration implementation cannot handle this situation.
> 
> This patch filters out the duplicated files; and adjust the size after
> the enumeration.
> 
> Fixes: 6a84c37e3975 ("net/virtio-user: add vhost-user adapter layer")
> 
> Signed-off-by: Jianfeng Tan <jianfeng.tan@intel.com>
> ---
>   .../howto/virtio_user_for_container_networking.rst |  3 ++-
>   drivers/net/virtio/virtio_user/vhost_user.c        | 28 ++++++++++++++++++++--
>   2 files changed, 28 insertions(+), 3 deletions(-)
> 
> diff --git a/doc/guides/howto/virtio_user_for_container_networking.rst b/doc/guides/howto/virtio_user_for_container_networking.rst
> index aa68b53..476ce3a 100644
> --- a/doc/guides/howto/virtio_user_for_container_networking.rst
> +++ b/doc/guides/howto/virtio_user_for_container_networking.rst
> @@ -109,7 +109,8 @@ We have below limitations in this solution:
>    * Cannot work with --no-huge option. Currently, DPDK uses anonymous mapping
>      under this option which cannot be reopened to share with vhost backend.
>    * Cannot work when there are more than VHOST_MEMORY_MAX_NREGIONS(8) hugepages.
> -   In another word, do not use 2MB hugepage so far.
> +   If you have more regions (especially when 2MB hugepages are used), the option,
> +   --single-file-segments, can help to reduce the number of shared files.
>    * Applications should not use file name like HUGEFILE_FMT ("%smap_%d"). That
>      will bring confusion when sharing hugepage files with backend by name.
>    * Root privilege is a must. DPDK resolves physical addresses of hugepages
> diff --git a/drivers/net/virtio/virtio_user/vhost_user.c b/drivers/net/virtio/virtio_user/vhost_user.c
> index a6df97a..01201c9 100644
> --- a/drivers/net/virtio/virtio_user/vhost_user.c
> +++ b/drivers/net/virtio/virtio_user/vhost_user.c
> @@ -138,12 +138,13 @@ struct hugepage_file_info {
>   static int
>   get_hugepage_file_info(struct hugepage_file_info huges[], int max)
>   {
> -	int idx;
> +	int idx, k, exist;
>   	FILE *f;
>   	char buf[BUFSIZ], *tmp, *tail;
>   	char *str_underline, *str_start;
>   	int huge_index;
>   	uint64_t v_start, v_end;
> +	struct stat stats;
>   
>   	f = fopen("/proc/self/maps", "r");
>   	if (!f) {
> @@ -183,16 +184,39 @@ get_hugepage_file_info(struct hugepage_file_info huges[], int max)
>   		if (sscanf(str_start, "map_%d", &huge_index) != 1)
>   			continue;
>   
> +		/* skip duplicated file which is mapped to different regions */
> +		for (k = 0, exist = -1; k < idx; ++k) {
> +			if (!strcmp(huges[k].path, tmp)) {
> +				exist = k;
> +				break;
> +			}
> +		}
> +		if (exist >= 0)
> +			continue;
> +
>   		if (idx >= max) {
>   			PMD_DRV_LOG(ERR, "Exceed maximum of %d", max);
>   			goto error;
>   		}
> +
>   		huges[idx].addr = v_start;
> -		huges[idx].size = v_end - v_start;
> +		huges[idx].size = v_end - v_start; /* To be corrected later */
>   		snprintf(huges[idx].path, PATH_MAX, "%s", tmp);
>   		idx++;
>   	}
>   
> +	/* correct the size for files who have many regions */
> +	for (k = 0; k < idx; ++k) {
> +		if (stat(huges[k].path, &stats) < 0) {
> +			PMD_DRV_LOG(ERR, "Failed to stat %s, %s\n",
> +				    huges[k].path, strerror(errno));
> +			continue;
> +		}
> +		huges[k].size = stats.st_size;
> +		PMD_DRV_LOG(INFO, "file %s, size %"PRIx64"\n",
> +			    huges[k].path, huges[k].size);
> +	}
> +
>   	fclose(f);
>   	return idx;
>   
> 

That sounds like potentially a lot of strcmp()'s (quadratic?). Can't it 
be sped up somehow? Maybe use rte_hash for storing this data?

-- 
Thanks,
Anatoly