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From: Philippe Proulx via lttng-dev <lttng-dev@lists.lttng.org>
To: RADERMACHER Ansgar <Ansgar.RADERMACHER@cea.fr>
Cc: "lttng-dev@lists.lttng.org" <lttng-dev@lists.lttng.org>
Subject: Re: [lttng-dev] [barectf] How to ensure that last events before a crash get recorded
Date: Fri, 5 Mar 2021 07:11:44 -0500	[thread overview]
Message-ID: <CAB4xu_38oAbOD606ZQCp71oJ8qwYOt7F1Ssmpk=idhhTM7to6w@mail.gmail.com> (raw)
In-Reply-To: <386C5D4D5C53C24CBC2C60CAAFD2136A5B4B2B92@EXDAG0-B1.intra.cea.fr>


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On Thu, Mar 4, 2021 at 10:28 RADERMACHER Ansgar via lttng-dev <
lttng-dev@lists.lttng.org> wrote:

> Hi,
>
> when doing tracing with barectf, the trace elements are written into a
> buffer first and only written when the buffer is full - or if the function
> barectf_platform_fs_fini gets called.
> In case of a crash, it's therefore possible to loose some events. What is
> the best option to prevent this issue? I've used signal handlers that call
> the function barectf_platform_fs_fini. This seems to work well with Linux,
> but is not portable. When using the provided sample platform, there is also
> the option to reduce the buffer size, but this is not ideal, as trace
> events that are too big for the buffer are not written.
>

First question: why are you using barectf on Linux vs LTTng?

LTTng supports writing the sub-buffers to NVRAM and, if the system crashes,
convert those sub-buffers to a CTF trace with the lttng-crash utility. See <
https://lttng.org/docs/v2.12/#doc-persistent-memory-file-systems>.

With NVRAM, you could do this with barectf with a corresponding platform
using it. It's always up to the platform author to decide where buffers are
and where complete packets go; it's not a feature of barectf as such.

Hope it helps,

Phil


> Best regards
>
> Ansgar
>
>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev@lists.lttng.org
> https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
>
-- 
Philippe Proulx

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  reply	other threads:[~2021-03-05 12:12 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-03-04 15:06 RADERMACHER Ansgar via lttng-dev
2021-03-05 12:11 ` Philippe Proulx via lttng-dev [this message]
2021-03-05 12:27   ` RADERMACHER Ansgar via lttng-dev

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