Re: [dpdk-stable] [dpdk-dev] [PATCH v5 1/1] fbarray: fix duplicated fbarray file in secondary

[Yasufumi Ogawa <yasufum.o@gmail.com>]

>> -----Original Message-----
>> From: Yasufumi Ogawa <yasufum.o@gmail.com>
>> Sent: Wednesday, October 30, 2019 1:42 PM
>> To: Ananyev, Konstantin <konstantin.ananyev@intel.com>; Burakov, Anatoly <anatoly.burakov@intel.com>; david.marchand@redhat.com
>> Cc: dev@dpdk.org; stable@dpdk.org; Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>> Subject: Re: [dpdk-dev] [PATCH v5 1/1] fbarray: fix duplicated fbarray file in secondary
>>
>> On 2019/10/29 21:03, Ananyev, Konstantin wrote:
>>>
>>>
>>>> -----Original Message-----
>>>> From: dev <dev-bounces@dpdk.org> On Behalf Of yasufum.o@gmail.com
>>>> Sent: Monday, October 28, 2019 8:08 AM
>>>> To: Burakov, Anatoly <anatoly.burakov@intel.com>; david.marchand@redhat.com
>>>> Cc: dev@dpdk.org; stable@dpdk.org; yasufum.o@gmail.com; Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>>>> Subject: [dpdk-dev] [PATCH v5 1/1] fbarray: fix duplicated fbarray file in secondary
>>>>
>>>> From: Yasufumi Ogawa <ogawa.yasufumi@lab.ntt.co.jp>
>>>>
>>>> In secondary_msl_create_walk(), it creates a file for fbarrays with its
>>>> PID for reserving unique name among secondary processes. However, it
>>>> does not work if several secondaries run as app containers because each
>>>> of containerized secondary has PID 1, and failed to reserve unique name
>>>> other than first one. To reserve unique name in each of containers, use
>>>> hostname instead of PID only if PID is 1.
>>>>
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Yasufumi Ogawa <yasufum.o@gmail.com>
>>>> ---
>>>>    lib/librte_eal/linux/eal/eal_memalloc.c | 15 +++++++++++++--
>>>>    1 file changed, 13 insertions(+), 2 deletions(-)
>>>>
>>>> diff --git a/lib/librte_eal/linux/eal/eal_memalloc.c b/lib/librte_eal/linux/eal/eal_memalloc.c
>>>> index af6d0d023..699079791 100644
>>>> --- a/lib/librte_eal/linux/eal/eal_memalloc.c
>>>> +++ b/lib/librte_eal/linux/eal/eal_memalloc.c
>>>> @@ -1365,6 +1365,7 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>>>>    	struct rte_memseg_list *primary_msl, *local_msl;
>>>>    	char name[PATH_MAX];
>>>>    	int msl_idx, ret;
>>>> +	char proc_id[HOST_NAME_MAX] = { 0 };
>>>>
>>>>    	if (msl->external)
>>>>    		return 0;
>>>> @@ -1374,8 +1375,18 @@ secondary_msl_create_walk(const struct rte_memseg_list *msl,
>>>>    	local_msl = &local_memsegs[msl_idx];
>>>>
>>>>    	/* create distinct fbarrays for each secondary */
>>>> -	snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%i",
>>>> -		primary_msl->memseg_arr.name, getpid());
>>>> +	/* If run secondary in a container, the name of fbarray file should
>>>> +	 * not be decided with pid because getpid() always returns 1.
>>>
>>>
>>> I wonder why is that?
>>> What will prevent user to do something like:
>>> docker run -it --cpuset-cpus=7-8 -v /local/kananye1:/local/kananye1 ubuntu-dpdk-local:latest /bin/bash
>>> And then start dpdk app manually within the container?
>> Hi Konstantin,
>>
>> Thank you for your comment.
>>
>> My concern is running secondary as app container. In current
>> implementation, the name of fbarray file is decided by using PID and it
>> must be overlapped with other process because assigning PID is started
>> from 1 in each of app container. This patch is to fix the issue.
>>
>> I think it is doable running app from bash for testing, but not
>> acceptable for a realistic usecase in which user manages several app
>> containers.
> 
> User can have a bash script to start inside container first, that
> would do some preparation work (setup env variables, etc.)....
> Or some different scenario when user needs/wants to
> spawn several processes within container.
I don't know how to avoid to overlap PID from bash script because I 
think PIDs on host cannot see from inside of a container. So, I'm not 
sure it is possible.

> Inside the lib you can't assume that your usage scenario is the
> only possible one.
I don't want to modify it for a specific usecase, but just to avoid to 
overlap filenames. I think it is better this filename is decided by lib 
itself without any of user configuration because user don't need to care 
about the file which is used by DPDK internally.

> I think solution needs to be generic enough to cover all such cases.

> BTW, why we can't always use hostname in fbarray format?
Sorry, I don't know. But I wonder using PID is more assured to get 
unique name, but does not work only for secondary app container 
accidentally.

Yasufumi
> 
>>
>> Regards,
>> Yasufumi
>>
>>>
>>>> +	 * In docker, hostname is assigned as a short form of full container
>>>> +	 * ID. So use hostname as unique ID among containers instead.
>>>> +	 */
>>>> +	if (getpid() == 1)
>>>> +		gethostname(proc_id, HOST_NAME_MAX);
>>>> +	else
>>>> +		sprintf(proc_id, "%d", (int)getpid());
>>>> +
>>>> +	snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%s",
>>>> +			primary_msl->memseg_arr.name, proc_id);
>>>>
>>>>    	ret = rte_fbarray_init(&local_msl->memseg_arr, name,
>>>>    		primary_msl->memseg_arr.len,
>>>> --
>>>> 2.17.1
>>>