From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers via lttng-dev Subject: Re: LTTng user-space callstacks Date: Thu, 26 Mar 2020 15:41:17 -0400 (EDT) Message-ID: <2022773652.13655.1585251677207.JavaMail.zimbra@efficios.com> References: Reply-To: Mathieu Desnoyers Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============6507115471348991421==" Return-path: Received: from mail.efficios.com (mail.efficios.com [167.114.26.124]) by lists.lttng.org (Postfix) with ESMTPS id 48pFjH3HP9z1Thj for ; Thu, 26 Mar 2020 15:41:23 -0400 (EDT) Received: from localhost (localhost [127.0.0.1]) by mail.efficios.com (Postfix) with ESMTP id 96A89279883 for ; Thu, 26 Mar 2020 15:41:17 -0400 (EDT) In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: lttng-dev-bounces@lists.lttng.org Sender: "lttng-dev" To: Valentin Grigorev Cc: lttng-dev List-Id: lttng-dev@lists.lttng.org --===============6507115471348991421== Content-Type: multipart/alternative; boundary="=_54626138-d6e6-456d-93fb-d5645f41ae4d" --=_54626138-d6e6-456d-93fb-d5645f41ae4d Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit ----- On Mar 26, 2020, at 1:39 PM, lttng-dev wrote: > Hello! > Currently, callstack collection in LTTng is only available for kernel-space > events with context fields callstack-kernel and callstack-user . > Is it expected that callstack collection for LTTng-UST will be added too? And if > it is expected, then how soon? Hi Valentin, It is something that would be interesting and useful, but a lot of work would be needed to have stack-walking this is fast enough and reentrant wrt signal handlers. Unfortunately, the backtrace(3) functions do not meet those requirements. Also, for gathering user-space callstacks from the kernel tracer, it only works if all user-space is compiled with frame pointers. This is also a limitation that would require a lot of work to overcome neatly. None of those features are currently on any roadmap due to lack of customers showing interest in getting this done. Thanks, Mathieu -- Mathieu Desnoyers EfficiOS Inc. http://www.efficios.com --=_54626138-d6e6-456d-93fb-d5645f41ae4d Content-Type: text/html; charset=utf-8 Content-Transfer-Encoding: quoted-printable

----- On Mar 26, 2020, at 1:39 PM, lttng-dev <lttng-dev@lists.lttng.= org> wrote:

Hello!

Curr= ently, callstack collection in LTTng is only available for kernel-spa= ce events with context fields callstack-kernel and call= stack-user.

Is it expected that callstack collection= for LTTng-UST will be added too? And if it is expected, then how soon?

Hi Valentin= ,

It is something that would be interesting an= d useful, but a lot of work would

be needed to have stack-walking= this is fast enough and reentrant wrt signal

handlers. Unfortuna= tely, the backtrace(3) functions do not meet those

requirements.<= /div>

Also, for gathering user-space callstacks from the= kernel tracer, it only works if

all user-space is compiled with = frame pointers. This is also a limitation that would

require a lo= t of work to overcome neatly.

None of those featur= es are currently on any roadmap due to lack of customers

showing = interest in getting this done.

Thanks,

<= br>

Mathieu

=

--

Mathieu Desnoyers
Ef= ficiOS Inc.
http://www.efficios.com

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