linux-kernel - Re: [PATCH v1 2/5] misc: fastrpc: Move all remote heap allocations to a new list

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Message-ID: <CAO9ioeUW=v_CBUchJEt3PArbzBbUgznFO8TK-j=2yUkv8S1Baw@mail.gmail.com>
Date: Thu, 22 May 2025 15:09:47 +0300
From: Dmitry Baryshkov <dmitry.baryshkov@....qualcomm.com>
To: Ekansh Gupta <ekansh.gupta@....qualcomm.com>
Cc: srinivas.kandagatla@....qualcomm.com, linux-arm-msm@...r.kernel.org,
        gregkh@...uxfoundation.org, quic_bkumar@...cinc.com,
        linux-kernel@...r.kernel.org, quic_chennak@...cinc.com,
        dri-devel@...ts.freedesktop.org, arnd@...db.de, stable@...nel.org,
        Alexey Klimov <alexey.klimov@...aro.org>
Subject: Re: [PATCH v1 2/5] misc: fastrpc: Move all remote heap allocations to
 a new list

On Thu, 22 May 2025 at 07:54, Ekansh Gupta
<ekansh.gupta@....qualcomm.com> wrote:
>
>
>
> On 5/19/2025 6:59 PM, Dmitry Baryshkov wrote:
> > On Mon, May 19, 2025 at 04:36:13PM +0530, Ekansh Gupta wrote:
> >>
> >> On 5/19/2025 3:46 PM, Dmitry Baryshkov wrote:
> >>> On Tue, May 13, 2025 at 09:58:22AM +0530, Ekansh Gupta wrote:
> >>>> Remote heap allocations are not organized in a maintainable manner,
> >>>> leading to potential issues with memory management. As the remote
> >>> Which issues? I think I have been asking this question previously.
> >>> Please expand the commit message here.
> >> This is mostly related to the memory clean-up and the other patch where
> >> unmap request was added, I'll try to pull more details about the issue
> >> scenario.
> > Thanks.
> >
> >>>> heap allocations are maintained in fl mmaps list, the allocations
> >>>> will go away if the audio daemon process is killed but there are
> >>> What is audio daemon process?
> >> As audio PD on DSP is static, there is HLOS process(audio daemon) required to
> >> attach to audio PD to fulfill it's memory and file operation requirements.
> >>
> >> This daemon can be thought of to be somewhat similar to rootPD(adsprpcd) or
> >> sensorsPD(sscrpcd) daemons. Although, there is a slight difference in case of audio
> >> daemon as it is required to take additional information and resources to audio PD
> >> while attaching.
> > I find it a little bit strange to see 'required' here, while we have
> > working audio setup on all up platforms up to and including SM8750
> > without any additional daemons. This is the primary reason for my
> > question: what is it, why is it necessary, when is it necessary, etc.
>
> This daemon is critical to facilitate dynamic loading and memory
> requirement for audio PD(running on DSP for audio processing). Even
> for audio testing on SM8750, I believe Alexey was enabling this daemon.

Could you please point out the daemon sources?

As far as I remember, we didn't need it on any of the platforms up to
and including SM8650, that's why I'm asking.

>
> What is it?
> - HLOS process to attached to audio PD to fulfill the requirements that
> cannot be met by DSP alone(like file operations, memory etc.)
>
> Why is it necessary?
> - There are limitation on DSP for which the PD requirements needs to be
> taken to HLOS. For example, DSP does not have it's own file system, so
> any file operation request it PD(say for dynamic loading) needs to be
> taken to HLOS(using listener/reverse calls) and is fulfilled there.
> Similarly memory requirement is another example.
>
> When is it necessary?
> - When audio PD needs to perform any task that requires HLOS relying
> operations like dynamic loading etc.

This doesn't exactly answer the question. I can play and capture audio
on most of the platforms that I tested without using extra daemon. So,
when is it necessary?


-- 
With best wishes
Dmitry