linux-kernel - Re: [PATCH v3 19/25] cxl/region/extent: Expose region extent information in sysfs

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Message-ID: <20240823181734.000022bb@Huawei.com>
Date: Fri, 23 Aug 2024 18:17:34 +0100
From: Jonathan Cameron <Jonathan.Cameron@...wei.com>
To: Ira Weiny <ira.weiny@...el.com>
CC: Dave Jiang <dave.jiang@...el.com>, Fan Ni <fan.ni@...sung.com>, "Navneet
 Singh" <navneet.singh@...el.com>, Chris Mason <clm@...com>, Josef Bacik
	<josef@...icpanda.com>, David Sterba <dsterba@...e.com>, Petr Mladek
	<pmladek@...e.com>, Steven Rostedt <rostedt@...dmis.org>, Andy Shevchenko
	<andriy.shevchenko@...ux.intel.com>, Rasmus Villemoes
	<linux@...musvillemoes.dk>, Sergey Senozhatsky <senozhatsky@...omium.org>,
	Jonathan Corbet <corbet@....net>, Andrew Morton <akpm@...ux-foundation.org>,
	Dan Williams <dan.j.williams@...el.com>, Davidlohr Bueso <dave@...olabs.net>,
	Alison Schofield <alison.schofield@...el.com>, Vishal Verma
	<vishal.l.verma@...el.com>, <linux-btrfs@...r.kernel.org>,
	<linux-cxl@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<linux-doc@...r.kernel.org>, <nvdimm@...ts.linux.dev>
Subject: Re: [PATCH v3 19/25] cxl/region/extent: Expose region extent
 information in sysfs

On Thu, 22 Aug 2024 21:58:02 -0500
Ira Weiny <ira.weiny@...el.com> wrote:

> Dave Jiang wrote:
> > 
> > 
> > On 8/16/24 7:44 AM, ira.weiny@...el.com wrote:  
> > > From: Navneet Singh <navneet.singh@...el.com>
> > > 
> > > Extent information can be helpful to the user to coordinate memory usage
> > > with the external orchestrator and FM.
> > > 
> > > Expose the details of region extents by creating the following
> > > sysfs entries.
> > > 
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/length
> > >         /sys/bus/cxl/devices/dax_regionX/extentX.Y/tag
> > > 
> > > Signed-off-by: Navneet Singh <navneet.singh@...el.com>
> > > Co-developed-by: Ira Weiny <ira.weiny@...el.com>
> > > Signed-off-by: Ira Weiny <ira.weiny@...el.com>
> > > 
> > > ---
> > > Changes:
> > > [iweiny: split this out]
> > > [Jonathan: add documentation for extent sysfs]
> > > [Jonathan/djbw: s/label/tag]
> > > [Jonathan/djbw: treat tag as uuid]
> > > [djbw: use __ATTRIBUTE_GROUPS]
> > > [djbw: make tag invisible if it is empty]
> > > [djbw/iweiny: use conventional id names for extents; extentX.Y]
> > > ---
> > >  Documentation/ABI/testing/sysfs-bus-cxl | 13 ++++++++
> > >  drivers/cxl/core/extent.c               | 58 +++++++++++++++++++++++++++++++++
> > >  2 files changed, 71 insertions(+)
> > > 
> > > diff --git a/Documentation/ABI/testing/sysfs-bus-cxl b/Documentation/ABI/testing/sysfs-bus-cxl
> > > index 3a5ee88e551b..e97e6a73c960 100644
> > > --- a/Documentation/ABI/testing/sysfs-bus-cxl
> > > +++ b/Documentation/ABI/testing/sysfs-bus-cxl
> > > @@ -599,3 +599,16 @@ Description:
> > >  		See Documentation/ABI/stable/sysfs-devices-node. access0 provides
> > >  		the number to the closest initiator and access1 provides the
> > >  		number to the closest CPU.
> > > +
> > > +What:		/sys/bus/cxl/devices/dax_regionX/extentX.Y/offset
> > > +		/sys/bus/cxl/devices/dax_regionX/extentX.Y/length
> > > +		/sys/bus/cxl/devices/dax_regionX/extentX.Y/tag  
> > 
> > I wonder consider an entry for each with their own descriptions, which seems to be the standard practice.  
> 
> :-/  Except kind of for the access'.
> 
> What:           /sys/bus/cxl/devices/regionZ/accessY/read_bandwidth
>                 /sys/bus/cxl/devices/regionZ/accessY/write_banwidth
> 
> What:           /sys/bus/cxl/devices/regionZ/accessY/read_latency
>                 /sys/bus/cxl/devices/regionZ/accessY/write_latency
> 
> But I think you have a point.

It's a balance between complexity and repetition.

E.g. https://elixir.bootlin.com/linux/v6.11-rc4/source/Documentation/ABI/testing/sysfs-bus-iio#L427
is one of these files I know far too well. That would be a lot
of very boring repetition and that doc is long enough without breaking them up.

Here there are only 3 and a good bit of description differs so
probably good to split up.

Less so for bandwidth and latency cases.

Jonathan

> 
> Ira
> 
> > 
> > DJ
> >   
> 
> [snip]
>