Re: [PATCH v4] dma-buf: Add DmaBufTotal counter in meminfo

[Peter.Enderborg]

On 4/19/21 2:16 PM, Michal Hocko wrote:
> On Sat 17-04-21 12:40:32, 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.
> The changelog would benefit from more background on why this is needed,
> and who is the primary consumer of that value.
>
> I cannot really comment on the dma-buf internals but I have two remarks.
> Documentation/filesystems/proc.rst needs an update with the counter
> explanation and secondly is this information useful for OOM situations
> analysis? If yes then show_mem should dump the value as well.
>
> From the implementation point of view, is there any reason why this
> hasn't used the existing global_node_page_state infrastructure?

I fix doc in next version.  Im not sure what you expect the commit message to include.

The function of the meminfo is: (From Documentation/filesystems/proc.rst)

"Provides information about distribution and utilization of memory."

Im not the designed of dma-buf, I think  global_node_page_state as a kernel
internal. dma-buf is a device driver that provides a function so I might be
on the outside. However I also see that it might be relevant for a OOM.
It is memory that can be freed by killing userspace processes.

The show_mem thing. Should it be a separate patch?