linux-kernel - Re: [PATCH v5] dma-buf: Add DmaBufTotal counter in meminfo

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Date:   Tue, 20 Apr 2021 14:52:26 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Peter.Enderborg@...y.com
Cc:     linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        sumit.semwal@...aro.org, christian.koenig@....com,
        adobriyan@...il.com, akpm@...ux-foundation.org,
        songmuchun@...edance.com, guro@...com, shakeelb@...gle.com,
        mhocko@...e.com, neilb@...e.de, samitolvanen@...gle.com,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, willy@...radead.org
Subject: Re: [PATCH v5] dma-buf: Add DmaBufTotal counter in meminfo

On Tue, Apr 20, 2021 at 10:45:21AM +0000, Peter.Enderborg@...y.com wrote:
> On 4/20/21 11:41 AM, Mike Rapoport wrote:
> > Hello Peter,
> >
> > On Tue, Apr 20, 2021 at 09:26:00AM +0000, Peter.Enderborg@...y.com wrote:
> >> On 4/20/21 10:58 AM, Daniel Vetter wrote:
> >>> On Sat, Apr 17, 2021 at 06:38:35PM +0200, Peter Enderborg wrote:
> >>>> This adds a total used dma-buf memory. Details
> >>>> can be found in debugfs, however it is not for everyone
> >>>> and not always available. dma-buf are indirect allocated by
> >>>> userspace. So with this value we can monitor and detect
> >>>> userspace applications that have problems.
> >>>>
> >>>> Signed-off-by: Peter Enderborg <peter.enderborg@...y.com>
> >>> So there have been tons of discussions around how to track dma-buf and
> >>> why, and I really need to understand the use-cass here first I think. proc
> >>> uapi is as much forever as anything else, and depending what you're doing
> >>> this doesn't make any sense at all:
> >>>
> >>> - on most linux systems dma-buf are only instantiated for shared buffer.
> >>>   So there this gives you a fairly meaningless number and not anything
> >>>   reflecting gpu memory usage at all.
> >>>
> >>> - on Android all buffers are allocated through dma-buf afaik. But there
> >>>   we've recently had some discussions about how exactly we should track
> >>>   all this, and the conclusion was that most of this should be solved by
> >>>   cgroups long term. So if this is for Android, then I don't think adding
> >>>   random quick stop-gaps to upstream is a good idea (because it's a pretty
> >>>   long list of patches that have come up on this).
> >>>
> >>> So what is this for?
> >> For the overview. dma-buf today only have debugfs for info. Debugfs
> >> is not allowed by google to use in andoid. So this aggregate the information
> >> so we can get information on what going on on the system. 
> >  
> > Can you send an example debugfs output to see what data are we talking
> > about?
> 
> Sure. This is on a idle system. Im not sure why you need it.The problem is partly that debugfs is
> not accessable on a commercial device.

I wanted to see what kind of information is there, but I didn't think it's
that long :)
 
> Dma-buf Objects:
> size        flags       mode        count       exp_name        buf name    ino    
> 00032768    00000002    00080007    00000002    ion-system-1006-allocator-servi    dmabuf17728    07400825    dmabuf17728
>     Attached Devices:
> Total 0 devices attached
> 
> 11083776    00000002    00080007    00000003    ion-system-1006-allocator-servi    dmabuf17727    07400824    dmabuf17727
>     Attached Devices:
>     ae00000.qcom,mdss_mdp:qcom,smmu_sde_unsec_cb
> Total 1 devices attached
> 
> 00032768    00000002    00080007    00000002    ion-system-1006-allocator-servi    dmabuf17726    07400823    dmabuf17726
>     Attached Devices:
> Total 0 devices attached
> 
> 11083776    00000002    00080007    00000002    ion-system-1006-allocator-servi    dmabuf17725    07400822    dmabuf17725
>     Attached Devices:
>     ae00000.qcom,mdss_mdp:qcom,smmu_sde_unsec_cb
> Total 1 devices attached

...

> Total 654 objects, 744144896 bytes
 
Isn't the size from the first column also available in fdinfo?

Is there anything that prevents monitoring those?

-- 
Sincerely yours,
Mike.