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

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Message-ID: <YH6bASnaRIV4DGpI@dhcp22.suse.cz>
Date:   Tue, 20 Apr 2021 11:12:33 +0200
From:   Michal Hocko <mhocko@...e.com>
To:     Peter.Enderborg@...y.com
Cc:     christian.koenig@....com, linux-kernel@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, sumit.semwal@...aro.org,
        adobriyan@...il.com, akpm@...ux-foundation.org,
        songmuchun@...edance.com, guro@...com, shakeelb@...gle.com,
        neilb@...e.de, samitolvanen@...gle.com, rppt@...nel.org,
        linux-media@...r.kernel.org, dri-devel@...ts.freedesktop.org,
        linaro-mm-sig@...ts.linaro.org, willy@...radead.org
Subject: Re: [PATCH v4] dma-buf: Add DmaBufTotal counter in meminfo

On Tue 20-04-21 09:02:57, Peter.Enderborg@...y.com wrote:
> 
> >> But that isn't really system memory at all, it's just allocated device
> >> memory.
> > OK, that was not really clear to me. So this is not really accounted to
> > MemTotal? If that is really the case then reporting it into the oom
> > report is completely pointless and I am not even sure /proc/meminfo is
> > the right interface either. It would just add more confusion I am
> > afraid.
> >  
> 
> Why is it confusing? Documentation is quite clear:

Because a single counter without a wider context cannot be put into any
reasonable context. There is no notion of the total amount of device
memory usable for dma-buf. As Christian explained some of it can be RAM
based. So a single number is rather pointless on its own in many cases.

Or let me just ask. What can you tell from dma-bud: $FOO kB in its
current form?
-- 
Michal Hocko
SUSE Labs