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

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

On 04-May-18 8:40 AM, Maxime Coquelin wrote:
> Hi Anatoly,
> 
> On 04/27/2018 11:31 AM, Burakov, Anatoly wrote:
>> 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?
>>
> 
> This patch is required to have virtio-user to work with 2MB pages.
> While it may be improved later, I think we should pick it for v18.05.
> Is it fine for you?

Looks fine to me otherwise.

> 
> Thanks,
> Maxime
> 


-- 
Thanks,
Anatoly