linux-kernel - Re: [PATCH] dmabuf: Add the capability to expose DMA-BUF stats in sysfs

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Message-ID: <X9H0JREcdxDsMtLX@kroah.com>
Date:   Thu, 10 Dec 2020 11:10:45 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Christian König <christian.koenig@....com>
Cc:     Hridya Valsaraju <hridya@...gle.com>,
        Sumit Semwal <sumit.semwal@...aro.org>,
        linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
        dri-devel@...ts.freedesktop.org, linaro-mm-sig@...ts.linaro.org,
        kernel-team@...roid.com, surenb@...gle.com, john.stultz@...aro.org
Subject: Re: [PATCH] dmabuf: Add the capability to expose DMA-BUF stats in
 sysfs

On Thu, Dec 10, 2020 at 10:58:50AM +0100, Christian König wrote:
> In general a good idea, but I have a few concern/comments here.
> 
> Am 10.12.20 um 05:43 schrieb Hridya Valsaraju:
> > This patch allows statistics to be enabled for each DMA-BUF in
> > sysfs by enabling the config CONFIG_DMABUF_SYSFS_STATS.
> > 
> > The following stats will be exposed by the interface:
> > 
> > /sys/kernel/dmabuf/<inode_number>/exporter_name
> > /sys/kernel/dmabuf/<inode_number>/size
> > /sys/kernel/dmabuf/<inode_number>/dev_map_info
> > 
> > The inode_number is unique for each DMA-BUF and was added earlier [1]
> > in order to allow userspace to track DMA-BUF usage across different
> > processes.
> > 
> > Currently, this information is exposed in
> > /sys/kernel/debug/dma_buf/bufinfo.
> > However, since debugfs is considered unsafe to be mounted in production,
> > it is being duplicated in sysfs.
> 
> Mhm, this makes it part of the UAPI. What is the justification for this?
> 
> In other words do we really need those debug information in a production
> environment?

Production environments seem to want to know who is using up memory :)