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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <YH6Ayy1fWGGWMU+q@kernel.org>
Date:   Tue, 20 Apr 2021 10:20:43 +0300
From:   Mike Rapoport <rppt@...nel.org>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Christian König <christian.koenig@....com>,
        Peter.Enderborg@...y.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,
        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, Apr 20, 2021 at 09:04:51AM +0200, Michal Hocko wrote:
> On Mon 19-04-21 18:37:13, Christian König wrote:
> > Am 19.04.21 um 18:11 schrieb Michal Hocko:
> [...]
> > > The question is not whether it is NUMA aware but whether it is useful to
> > > know per-numa data for the purpose the counter is supposed to serve.
> > 
> > No, not at all. The pages of a single DMA-buf could even be from different
> > NUMA nodes if the exporting driver decides that this is somehow useful.
> 
> As the use of the counter hasn't been explained yet I can only
> speculate. One thing that I can imagine to be useful is to fill gaps in
> our accounting. It is quite often that the memroy accounted in
> /proc/meminfo (or oom report) doesn't add up to the overall memory
> usage. In some workloads the workload can be huge! In many cases there
> are other means to find out additional memory by a subsystem specific
> interfaces (e.g. networking buffers). I do assume that dma-buf is just
> one of those and the counter can fill the said gap at least partially
> for some workloads. That is definitely useful.

A bit off-topic.

Michal, I think it would have been nice to have an explanation like above
in Documentation/proc/meminfo, what do you say?
 
> What I am trying to bring up with NUMA side is that the same problem can
> happen on per-node basis. Let's say that some user consumes unexpectedly
> large amount of dma-buf on a certain node. This can lead to observable
> performance impact on anybody on allocating from that node and even
> worse cause an OOM for node bound consumers. How do I find out that it
> was dma-buf that has caused the problem?
> 
> See where I am heading?

-- 
Sincerely yours,
Mike.