linux-kernel - Re: [PATCH v3 0/7] Statsfs: a new ram-based file system for Linux kernel statistics

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Message-ID: <b0d11337-3ea4-d874-6013-ff8c3e9d6f26@redhat.com>
Date:   Wed, 27 May 2020 17:00:41 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Andrew Lunn <andrew@...n.ch>,
        Emanuele Giuseppe Esposito <eesposit@...hat.com>
Cc:     Jakub Kicinski <kuba@...nel.org>, kvm@...r.kernel.org,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Jim Mattson <jmattson@...gle.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Emanuele Giuseppe Esposito <e.emanuelegiuseppe@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        Jonathan Adams <jwadams@...gle.com>, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mips@...r.kernel.org, kvm-ppc@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, linux-s390@...r.kernel.org,
        linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v3 0/7] Statsfs: a new ram-based file system for Linux
 kernel statistics

On 27/05/20 15:33, Andrew Lunn wrote:
>> I don't really know a lot about the networking subsystem, and as it was
>> pointed out in another email on patch 7 by Andrew, networking needs to
>> atomically gather and display statistics in order to make them consistent,
>> and currently this is not supported by stats_fs but could be added in
>> future.
> 
> Do you have any idea how you will support atomic access? It does not
> seem easy to implement in a filesystem based model.

Hi Andrew,

there are plans to support binary access.  Emanuele and I don't really
have a plan for how to implement it, but there are developers from
Google that have ideas (because Google has a similar "metricfs" thing
in-house).

I think atomic access would use some kind of "source_ops" struct
containing create_snapshot and release_snapshot function pointers.

Paolo