When the trace buffers are saved to disk?

When the trace buffers are saved to disk?

[Adel Belkhiri]

[-- Attachment #1: Type: text/plain, Size: 710 bytes --]

Hi all,

Recently, while tracing applications from the apps and examples
directories, I became confused about when the trace buffer is written to
disk. Is the trace data saved only when rte_save_trace() is called, or does
it also automatically save when the buffer becomes full?

From my understanding, rte_save_trace() is invoked when the application
executes rte_eal_cleanup(). Does this mean the target application needs to
explicitly support tracing by calling rte_save_trace()—perhaps at regular
intervals—to dump the trace buffer to disk? Otherwise, will we only get a
fragment of the trace saved during rte_eal_cleanup() execution?

Thank you for clarifying this point.

Best,
Adel

[-- Attachment #2: Type: text/html, Size: 742 bytes --]

Re: When the trace buffers are saved to disk?

[Thomas Monjalon]

28/11/2024 20:17, Adel Belkhiri:
> Hi all,
> 
> Recently, while tracing applications from the apps and examples
> directories, I became confused about when the trace buffer is written to
> disk. Is the trace data saved only when rte_save_trace() is called, or does

It is rte_trace_save()

> it also automatically save when the buffer becomes full?

No, DPDK is not doing such thing without user agreement.

> From my understanding, rte_save_trace() is invoked when the application
> executes rte_eal_cleanup(). Does this mean the target application needs to
> explicitly support tracing by calling rte_save_trace()—perhaps at regular
> intervals—to dump the trace buffer to disk? Otherwise, will we only get a
> fragment of the trace saved during rte_eal_cleanup() execution?

Yes you get it right.

> Thank you for clarifying this point.

Thanks for asking.

If you think the doc below is not clear enough,
do not hesitate to submit a patch to make the doc better:

	https://doc.dpdk.org/guides/prog_guide/trace_lib.html

Re: When the trace buffers are saved to disk?

[Adel Belkhiri]

[-- Attachment #1: Type: text/plain, Size: 1473 bytes --]

Thank you for the clarification, Thomas. Indeed, the documentation for the
trace library is kind of limited. If you don't mind, I have another
question: Would it be useful to have an API to register a callback (to save
trace data) when the buffer is full?

On Fri, Nov 29, 2024 at 6:44 AM Thomas Monjalon <thomas@monjalon.net> wrote:

> 28/11/2024 20:17, Adel Belkhiri:
> > Hi all,
> >
> > Recently, while tracing applications from the apps and examples
> > directories, I became confused about when the trace buffer is written to
> > disk. Is the trace data saved only when rte_save_trace() is called, or
> does
>
> It is rte_trace_save()
>
> > it also automatically save when the buffer becomes full?
>
> No, DPDK is not doing such thing without user agreement.
>
> > From my understanding, rte_save_trace() is invoked when the application
> > executes rte_eal_cleanup(). Does this mean the target application needs
> to
> > explicitly support tracing by calling rte_save_trace()—perhaps at regular
> > intervals—to dump the trace buffer to disk? Otherwise, will we only get a
> > fragment of the trace saved during rte_eal_cleanup() execution?
>
> Yes you get it right.
>
> > Thank you for clarifying this point.
>
> Thanks for asking.
>
> If you think the doc below is not clear enough,
> do not hesitate to submit a patch to make the doc better:
>
>         https://doc.dpdk.org/guides/prog_guide/trace_lib.html
>
>
>
>

[-- Attachment #2: Type: text/html, Size: 1981 bytes --]

Re: When the trace buffers are saved to disk?

[Thomas Monjalon]

29/11/2024 21:39, Adel Belkhiri:
> Thank you for the clarification, Thomas. Indeed, the documentation for the
> trace library is kind of limited. If you don't mind, I have another
> question: Would it be useful to have an API to register a callback (to save
> trace data) when the buffer is full?

I suppose yes, the problem being which thread is running file writing.

I leave it to the maintainers of the trace library.


> On Fri, Nov 29, 2024 at 6:44 AM Thomas Monjalon <thomas@monjalon.net> wrote:
> > 28/11/2024 20:17, Adel Belkhiri:
> > > Hi all,
> > >
> > > Recently, while tracing applications from the apps and examples
> > > directories, I became confused about when the trace buffer is written to
> > > disk. Is the trace data saved only when rte_save_trace() is called, or
> > does
> >
> > It is rte_trace_save()
> >
> > > it also automatically save when the buffer becomes full?
> >
> > No, DPDK is not doing such thing without user agreement.
> >
> > > From my understanding, rte_save_trace() is invoked when the application
> > > executes rte_eal_cleanup(). Does this mean the target application needs
> > to
> > > explicitly support tracing by calling rte_save_trace()—perhaps at regular
> > > intervals—to dump the trace buffer to disk? Otherwise, will we only get a
> > > fragment of the trace saved during rte_eal_cleanup() execution?
> >
> > Yes you get it right.
> >
> > > Thank you for clarifying this point.
> >
> > Thanks for asking.
> >
> > If you think the doc below is not clear enough,
> > do not hesitate to submit a patch to make the doc better:
> >
> >         https://doc.dpdk.org/guides/prog_guide/trace_lib.html

Re: When the trace buffers are saved to disk?

[Adel Belkhiri]

[-- Attachment #1: Type: text/plain, Size: 1929 bytes --]

Thank you for your answer.

On Fri, Nov 29, 2024 at 4:23 PM Thomas Monjalon <thomas@monjalon.net> wrote:

> 29/11/2024 21:39, Adel Belkhiri:
> > Thank you for the clarification, Thomas. Indeed, the documentation for
> the
> > trace library is kind of limited. If you don't mind, I have another
> > question: Would it be useful to have an API to register a callback (to
> save
> > trace data) when the buffer is full?
>
> I suppose yes, the problem being which thread is running file writing.
>
> I leave it to the maintainers of the trace library.
>
>
> > On Fri, Nov 29, 2024 at 6:44 AM Thomas Monjalon <thomas@monjalon.net>
> wrote:
> > > 28/11/2024 20:17, Adel Belkhiri:
> > > > Hi all,
> > > >
> > > > Recently, while tracing applications from the apps and examples
> > > > directories, I became confused about when the trace buffer is
> written to
> > > > disk. Is the trace data saved only when rte_save_trace() is called,
> or
> > > does
> > >
> > > It is rte_trace_save()
> > >
> > > > it also automatically save when the buffer becomes full?
> > >
> > > No, DPDK is not doing such thing without user agreement.
> > >
> > > > From my understanding, rte_save_trace() is invoked when the
> application
> > > > executes rte_eal_cleanup(). Does this mean the target application
> needs
> > > to
> > > > explicitly support tracing by calling rte_save_trace()—perhaps at
> regular
> > > > intervals—to dump the trace buffer to disk? Otherwise, will we only
> get a
> > > > fragment of the trace saved during rte_eal_cleanup() execution?
> > >
> > > Yes you get it right.
> > >
> > > > Thank you for clarifying this point.
> > >
> > > Thanks for asking.
> > >
> > > If you think the doc below is not clear enough,
> > > do not hesitate to submit a patch to make the doc better:
> > >
> > >         https://doc.dpdk.org/guides/prog_guide/trace_lib.html
>
>
>
>

[-- Attachment #2: Type: text/html, Size: 2726 bytes --]

RE: [EXTERNAL] Re: When the trace buffers are saved to disk?

[Jerin Jacob]

> -----Original Message-----
> From: Adel Belkhiri <adel.belkhiri@gmail.com>
> Sent: Saturday, November 30, 2024 2:55 AM
> To: Thomas Monjalon <thomas@monjalon.net>
> Cc: dev@dpdk.org; Jerin Jacob <jerinj@marvell.com>; Sunil Kumar Kori
> <skori@marvell.com>
> Subject: [EXTERNAL] Re: When the trace buffers are saved to disk?
> 
> Thank you for your answer. On Fri, Nov 29, 2024 at 4: 23 PM Thomas Monjalon
> <thomas@ monjalon. net> wrote: 29/11/2024 21: 39, Adel Belkhiri: > Thank you
> for the clarification, Thomas. Indeed, the documentation for the > trace library
> 
> Thank you for your answer.
> 
> On Fri, Nov 29, 2024 at 4:23 PM Thomas Monjalon <thomas@monjalon.net
> <mailto:thomas@monjalon.net> > wrote:
> 
> 
> 	29/11/2024 21:39, Adel Belkhiri:
> 	> Thank you for the clarification, Thomas. Indeed, the documentation
> for the
> 	> trace library is kind of limited. If you don't mind, I have another
> 	> question: Would it be useful to have an API to register a callback (to
> save
> 	> trace data) when the buffer is full?
> 
> 	I suppose yes, the problem being which thread is running file writing.

Each thread has separate channels i.e  separate memory. it is OK.

Main problem will be it can stall trace emission (e.s.p in fastpath) as these medium
(storage or network) will be slow to transfer.




> 
> 	I leave it to the maintainers of the trace library.
> 
> 
> 	> On Fri, Nov 29, 2024 at 6:44 AM Thomas Monjalon
> <thomas@monjalon.net <mailto:thomas@monjalon.net> > wrote:
> 	> > 28/11/2024 20:17, Adel Belkhiri:
> 	> > > Hi all,
> 	> > >
> 	> > > Recently, while tracing applications from the apps and examples
> 	> > > directories, I became confused about when the trace buffer is
> written to
> 	> > > disk. Is the trace data saved only when rte_save_trace() is called,
> or
> 	> > does
> 	> >
> 	> > It is rte_trace_save()
> 	> >
> 	> > > it also automatically save when the buffer becomes full?
> 	> >
> 	> > No, DPDK is not doing such thing without user agreement.
> 	> >
> 	> > > From my understanding, rte_save_trace() is invoked when the
> application
> 	> > > executes rte_eal_cleanup(). Does this mean the target application
> needs
> 	> > to
> 	> > > explicitly support tracing by calling rte_save_trace()—perhaps at
> regular
> 	> > > intervals—to dump the trace buffer to disk? Otherwise, will we
> only get a
> 	> > > fragment of the trace saved during rte_eal_cleanup() execution?
> 	> >
> 	> > Yes you get it right.
> 	> >
> 	> > > Thank you for clarifying this point.
> 	> >
> 	> > Thanks for asking.
> 	> >
> 	> > If you think the doc below is not clear enough,
> 	> > do not hesitate to submit a patch to make the doc better:
> 	> >
> 	> >         https://doc.dpdk.org/guides/prog_guide/trace_lib.html
> <https://urldefense.proofpoint.com/v2/url?u=https-
> 3A__doc.dpdk.org_guides_prog-5Fguide_trace-
> 5Flib.html&d=DwMFaQ&c=nKjWec2b6R0mOyPaz7xtfQ&r=1DGob4H4rxz6H8uIT
> ozGOCa0s5f4wCNtTa4UUKvcsvI&m=PK0ws3Dbdr_mMLx2eKS2mDDFfgTq6zBtfr
> VM5C6twScLE3HMylemVgzhtcl_YzoO&s=E7gtIuTFNmRwZ_mZBpAI9PjOKZYpvW
> Mytuj_TdSkLvE&e=>
> 
> 
> 
>