Re: [PATCH] docs: proc.rst: meminfo: briefly describe gaps in memory accounting

[Mike Rapoport <rppt@kernel.org>]

On Tue, Apr 20, 2021 at 11:10:03AM +0200, Michal Hocko wrote:
> On Tue 20-04-21 11:51:05, Mike Rapoport wrote:
> > From: Mike Rapoport <rppt@linux.ibm.com>
> 
> Some trivial changelog would be better than nothing.
 
oh, sure.

> > Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> 
> But I do agree that this is a useful information to have in the
> documentation. Having networking counters as an example is helpful as
> well. I am not familiar with those myself much and I do remember there
> is much to it than just sockstat. It would be great to consult this with
> some networking expert and extend the documentation for that case which
> tends to be quite common AFAIK.
 
I've found a citation from one of Eric Dumazet's emails [1], and used that
instead:

... subsystem specific interfaces, for instance /proc/net/sockstat for TCP
memory allocations

[1] https://lore.kernel.org/lkml/CANn89iKprp7WYeZy4RRO5jHykprnSCcVBc7Tk14Ui_MA9OK7Fg@mail.gmail.com

> Anyway this is already an improvement and a step into the right
> direction.
> 
> Acked-by: Michal Hocko <mhocko@suse.com>
> 
> one nit below
> > ---
> >  Documentation/filesystems/proc.rst | 11 +++++++++--
> >  1 file changed, 9 insertions(+), 2 deletions(-)
> > 
> > diff --git a/Documentation/filesystems/proc.rst b/Documentation/filesystems/proc.rst
> > index 48fbfc336ebf..bf245151645b 100644
> > --- a/Documentation/filesystems/proc.rst
> > +++ b/Documentation/filesystems/proc.rst
> > @@ -929,8 +929,15 @@ meminfo
> >  ~~~~~~~
> >  
> >  Provides information about distribution and utilization of memory.  This
> > -varies by architecture and compile options.  The following is from a
> > -16GB PIII, which has highmem enabled.  You may not have all of these fields.
> > +varies by architecture and compile options. Please note that is may happen
> 
> that it may happen

Right.
 
> > +that the memory accounted here does not add up to the overall memory usage
> > +and the difference for some workloads can be substantial. In many cases
> > +there are other means to find out additional memory using subsystem
> > +specific interfaces, for instance /proc/net/sockstat for networking
> > +buffers.
> > +
> > +The following is from a 16GB PIII, which has highmem enabled.
> > +You may not have all of these fields.
> >  
> >  ::
> >  
> > -- 
> > 2.29.2
> 
> -- 
> Michal Hocko
> SUSE Labs

-- 
Sincerely yours,
Mike.