Re: [dpdk-stable] [PATCH v6 1/1] fbarray: fix duplicated fbarray file in secondary

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

>>> -----Original Message-----
>>> From: Burakov, Anatoly <anatoly.burakov@intel.com>
>>> Sent: Tuesday, November 5, 2019 11:31 AM
>>> To: David Marchand <david.marchand@redhat.com>; Yasufumi Ogawa 
>>> <yasufum.o@gmail.com>
>>> Cc: Ananyev, Konstantin <konstantin.ananyev@intel.com>; dev 
>>> <dev@dpdk.org>; dpdk stable <stable@dpdk.org>; Yasufumi Ogawa
>>> <ogawa.yasufumi@lab.ntt.co.jp>
>>> Subject: Re: [PATCH v6 1/1] fbarray: fix duplicated fbarray file in 
>>> secondary
>>>
>>> On 05-Nov-19 10:13 AM, David Marchand wrote:
>>>> Hello Anatoly, Yasufumi,
>>>>
>>>> On Mon, Nov 4, 2019 at 11:20 AM Burakov, Anatoly
>>>> <anatoly.burakov@intel.com> wrote:
>>>>>
>>>>> On 01-Nov-19 9:04 AM, yasufum.o@gmail.com wrote:
>>>>>> 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 in addition to PID.
>>>>>>
>>>>>> Cc: stable@dpdk.org
>>>>
>>>> We can't backport this as is, see below.
>>>>
>>>>
>>>>>>
>>>>>> Signed-off-by: Yasufumi Ogawa <yasufum.o@gmail.com>
>>>>>> ---
>>>>>>     lib/librte_eal/common/include/rte_fbarray.h |  2 +-
>>>>>>     lib/librte_eal/linux/eal/eal_memalloc.c     | 11 ++++++++---
>>>>>>     2 files changed, 9 insertions(+), 4 deletions(-)
>>>>>>
>>>>>> diff --git a/lib/librte_eal/common/include/rte_fbarray.h 
>>>>>> b/lib/librte_eal/common/include/rte_fbarray.h
>>>>>> index 6dccdbec9..5c2815093 100644
>>>>>> --- a/lib/librte_eal/common/include/rte_fbarray.h
>>>>>> +++ b/lib/librte_eal/common/include/rte_fbarray.h
>>>>>> @@ -39,7 +39,7 @@ extern "C" {
>>>>>>     #include <rte_compat.h>
>>>>>>     #include <rte_rwlock.h>
>>>>>>
>>>>>> -#define RTE_FBARRAY_NAME_LEN 64
>>>>>> +#define RTE_FBARRAY_NAME_LEN NAME_MAX
>>>>
>>>> The change on RTE_FBARRAY_NAME_LEN breaks the ABI, so we cannot
>>>> backport this as is.
>>>> For 19.11, we can allow this breakage, but we need an update of the
>>>> release notes.
OK. I wasn't careful for the ABI change. I think RTE_FBARRAY_NAME_LEN 64 
is enough without using hostname as a part of fbarray. So I would like 
to discard this change.

>>>>
>>>> Besides, what is the impact in terms of memory consumption?
>>>>
>>>>
>>>>>>
>>>>>>     struct rte_fbarray {
>>>>>>         char name[RTE_FBARRAY_NAME_LEN]; /**< name associated with 
>>>>>> an array */
>>>>>> diff --git a/lib/librte_eal/linux/eal/eal_memalloc.c 
>>>>>> b/lib/librte_eal/linux/eal/eal_memalloc.c
>>>>>> index af6d0d023..24f0275c9 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 hostname[HOST_NAME_MAX] = { 0 };
>>>>>>
>>>>>>         if (msl->external)
>>>>>>                 return 0;
>>>>>> @@ -1373,9 +1374,13 @@ secondary_msl_create_walk(const struct 
>>>>>> rte_memseg_list *msl,
>>>>>>         primary_msl = &mcfg->memsegs[msl_idx];
>>>>>>         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());
>>>>>> +     /* Create distinct fbarrays for each secondary by using PID and
>>>>>> +      * hostname. The reason why using hostname is because PID 
>>>>>> could be
>>>>>> +      * duplicated among secondaries if it is launched in a 
>>>>>> container.
>>>>>> +      */
>>>>>> +     gethostname(hostname, HOST_NAME_MAX);
>>>>
>>>> Personal preference, s/HOST_NAME_MAX/sizeof(hostname)/.
>>>>
>>>>
>>>> hostname[] is HOST_NAME_MAX bytes long.
>>>> In the worst case, we can get a non NULL terminated hostname string.
>>>> "
>>>>          gethostname() returns the null-terminated hostname in the
>>>> character array name, which has a length of len bytes.  If the
>>>> null-terminated hostname is too large to fit, then the name is
>>>> truncated, and
>>>>          no error is returned (but see NOTES below).  POSIX.1-2001 says
>>>> that if such truncation occurs, then it is unspecified whether the
>>>> returned buffer includes a terminating null byte.
>>>> ...
>>>> NOTES
>>>>          SUSv2 guarantees that "Host names are limited to 255 bytes".
>>>> POSIX.1-2001 guarantees that "Host names (not including the
>>>> terminating null byte) are  limited  to  HOST_NAME_MAX  bytes".   On
>>>> Linux,
>>>>          HOST_NAME_MAX is defined with the value 64, which has been the
>>>> limit since Linux 1.0 (earlier kernels imposed a limit of 8 bytes).
>>>> "
>>>>
>>>> How about making hostname[] HOST_NAME_MAX+1 bytes long?
>>>>
>>>>>> +     snprintf(name, RTE_FBARRAY_NAME_LEN, "%s_%s_%d",
>>>>>> +                     primary_msl->memseg_arr.name, hostname, 
>>>>>> (int)getpid());
>>>>>>
>>>>>>         ret = rte_fbarray_init(&local_msl->memseg_arr, name,
>>>>>>                 primary_msl->memseg_arr.len,
>>>>>>
>>>>>
>>>>> I think the order should be reversed. Both containers and 
>>>>> non-containers
>>>>> can have their hostname set, and RTE_FBARRAY_NAME_LEN is of fairly
>>>>> limited length, so if the hostname is long enough, the PID never gets
>>>>> into the name string, resulting in duplicates. It is better have 
>>>>> pid first.
>>>>
>>>> Anatoly,
>>>>
>>>> On the principle, it seems better, yes.
>>>> Just the comment on RTE_FBARRAY_NAME_LEN indicates that you missed the
>>>> change at the top of the patch.
>>>> What do you think of this change?
>>>>
>>>
>>> Yes, i did miss that, apologies.
>>>
>>> I don't have a strong opinion on this change, however the above comment
>>> would still be true if we make fbarray size to be hostname_max + 1 - we
>>> still potentially get no space for a pid. So if we're going to have pid
>>> in there as well, it should be hostname_max + pid_max (5 digits?) +
>>> whatever underscores we have + null terminator, to ensure it fits under
>>> any and all circumstances.#
In "man 5 proc", it says the default value of pid_max is 32768, but can 
be set up to 2^22 (=4194304) on 64-bit systems. So, I think it is safer 
to consider pid_max is 7 digits.

I can find secondary's fbarray file named as
$ sudo ls /var/run/dpdk/rte/
...
fbarray_memseg-1048576k-0-0_24118
fbarray_memseg-1048576k-0-0_24191
fbarray_memseg-1048576k-0-0_24199
...

It consists of [prefix]-[hugepage size]-[numa node?]-[memchan?]_[PID]", 
and size of the name before PID is totally 28 digits. If another 
underscore and hostname are included in the name, the max size of 
fbarray file name is
   28 + 7(PID) + 1(underscore) + HOST_NAME_MAX+1(null terminator)

Considering 28 can be larger, how about using 32 as following?
+     int fbarray_sec_name_len = 32 + 7 + 1 + HOST_NAME_MAX + 1;

+     snprintf(name, fbarray_sec_name_len, "%s_%d_%s",
+                     primary_msl->memseg_arr.name, getpid(), hostname);

>>
>> I think that at least on linux we have more than enough space here:
>>
>> $ find /usr/include -type f | xargs grep ' NAME_MAX' | grep define
>> /usr/include/linux/limits.h:#define NAME_MAX         255        /* # 
>> chars in a file name */
>>
>> $ find /usr/include -type f | xargs grep ' HOST_NAME_MAX' | grep define
>> /usr/include/i386-linux-gnu/bits/local_lim.h:#define 
>> HOST_NAME_MAX             64
>> /usr/include/x86_64-linux-gnu/bits/local_lim.h:#define 
>> HOST_NAME_MAX           64
>>
> 
> Okay, works for me :)

Thanks,
Yasufumi