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From: Mattias Rönnblom <mattias.ronnblom@ericsson.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com>,
	"Van Haaren, Harry" <harry.van.haaren@intel.com>,
	dpdk-dev <dev@dpdk.org>,
	Tomasz Piatkowski <tomasz.piatkowski@ericsson.com>,
	nd <nd@arm.com>
Subject: Re: [dpdk-dev] Retrieving lcore worker thread id
Date: Thu, 16 Jul 2020 10:20:29 +0000
Message-ID: <8df56fc2-781a-a2dd-c8b8-87696299b921@ericsson.com> (raw)
In-Reply-To: <20200715092120.67e28eae@hermes.lan>

On 2020-07-15 18:21, Stephen Hemminger wrote:
> On Wed, 15 Jul 2020 10:17:09 +0000
> Mattias Rönnblom <mattias.ronnblom@ericsson.com> wrote:
>> On 2020-07-14 22:51, Stephen Hemminger wrote:
>>> On Tue, 14 Jul 2020 18:59:59 +0000
>>> Honnappa Nagarahalli <Honnappa.Nagarahalli@arm.com> wrote:
>>>> <snip>
>>>>>> Hi.
>>>>> Hey,
>>>>>> In DPDK 19.11, the lcore_config struct of <rte_lcore.h> is made
>>>>>> private, and with it the possibility to look up the thread id of the
>>>>>> lcore worker threads disappears.
>>>>>> One use case is an application with a monitoring function (on some
>>>>>> control plane thread), which uses the thread ids to make sure the
>>>>>> worker threads gets the CPU runtime they should, and thus is able to
>>>>>> detect stalls.
>>>> This sounds similar to 'keep alive' functionality.
>>>>>> Is there some other way of finding out the thread_id of a lcore worker
>>>>>> thread? All I can think of are hacks like using a temporary service
>>>>>> function for service cores, in combination with requiring launched
>>>>>> application threads also to store their thread id in some global
>>>>>> structure (index by lcore_id).
>>>>> -1 for the service cores idea. I like the creative solution thinking, but not as a
>>>>> long-term solution.
>>>>>> Is there some cleaner way? If not, would adding something like a
>>>>>> rte_lcore_thread_id() function make sense?
>>>> I guess here you mean the OS provided thread ID. Are there OS calls that provide the CPU runtime?
>>> This might be difficult sinc thread id in Linux/glibc is intentionally and opaque value.
>>> According to Posix the only valid way to look at it is to use return value from
>>> pthread_create() and pthread_self().
>> The rte_lcore_thread_id() would return this value, which could
>> subsequently be used in the application, calling pthread_getcpuclockid()
>> and clock_gettime() to retrieve the run time for the lcore worker
>> thread. No need to break the opacity in this case, although the Linux
>> thread id (i.e. the result of a gettid()) would be useful in case you
>> would want to dig around in /proc for other scheduler statistics.
>> Regards,
>>       Mattias
> The issue is glibc doesn't want to allow gettid()
> there is no wrapper, the only way to get it is using syscall()

There was certainly a lot of reluctance to add it, but since glibc 2.30, 
there is a syscall wrapper in place.

  reply	other threads:[~2020-07-16 10:20 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-14 12:03 Mattias Rönnblom
2020-07-14 13:08 ` Van Haaren, Harry
2020-07-14 18:59   ` Honnappa Nagarahalli
2020-07-14 20:51     ` Stephen Hemminger
2020-07-15 10:17       ` Mattias Rönnblom
2020-07-15 16:21         ` Stephen Hemminger
2020-07-16 10:20           ` Mattias Rönnblom [this message]
2020-08-10  9:36             ` [dpdk-dev] [RFC] eal: introduce function to get lcore " Mattias Rönnblom
2020-10-20 13:38               ` David Marchand
2020-10-20 18:40                 ` Mattias Rönnblom
2020-07-15 10:21   ` [dpdk-dev] Retrieving lcore worker " Mattias Rönnblom

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