netdev - RE: [RFC PATCH v12 17/17] dlb: add basic sysfs interfaces

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Message-ID: <CO1PR11MB5170DC5C16ADE17DA4C5AD0FD97D9@CO1PR11MB5170.namprd11.prod.outlook.com>
Date:   Wed, 22 Dec 2021 04:21:06 +0000
From:   "Chen, Mike Ximing" <mike.ximing.chen@...el.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "arnd@...db.de" <arnd@...db.de>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "Williams, Dan J" <dan.j.williams@...el.com>,
        "pierre-louis.bossart@...ux.intel.com" 
        <pierre-louis.bossart@...ux.intel.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>
Subject: RE: [RFC PATCH v12 17/17] dlb: add basic sysfs interfaces



> -----Original Message-----
> From: Stephen Hemminger <stephen@...workplumber.org>
> Sent: Tuesday, December 21, 2021 6:35 PM
> To: Chen, Mike Ximing <mike.ximing.chen@...el.com>
> Cc: linux-kernel@...r.kernel.org; arnd@...db.de; gregkh@...uxfoundation.org; Williams, Dan J
> <dan.j.williams@...el.com>; pierre-louis.bossart@...ux.intel.com; netdev@...r.kernel.org;
> davem@...emloft.net; kuba@...nel.org
> Subject: Re: [RFC PATCH v12 17/17] dlb: add basic sysfs interfaces
> 
> On Tue, 21 Dec 2021 00:50:47 -0600
> Mike Ximing Chen <mike.ximing.chen@...el.com> wrote:
> 
> > The dlb sysfs interfaces include files for reading the total and
> > available device resources, and reading the device ID and version. The
> > interfaces are used for device level configurations and resource
> > inquiries.
> >
> > Signed-off-by: Mike Ximing Chen <mike.ximing.chen@...el.com>
> > ---
> >  Documentation/ABI/testing/sysfs-driver-dlb | 116 ++++++++++++
> >  drivers/misc/dlb/dlb_args.h                |  34 ++++
> >  drivers/misc/dlb/dlb_main.c                |   5 +
> >  drivers/misc/dlb/dlb_main.h                |   3 +
> >  drivers/misc/dlb/dlb_pf_ops.c              | 195 +++++++++++++++++++++
> >  drivers/misc/dlb/dlb_resource.c            |  50 ++++++
> >  6 files changed, 403 insertions(+)
> >  create mode 100644 Documentation/ABI/testing/sysfs-driver-dlb
> >
> > diff --git a/Documentation/ABI/testing/sysfs-driver-dlb
> > b/Documentation/ABI/testing/sysfs-driver-dlb
> > new file mode 100644
> > index 000000000000..bf09ef6f8a3a
> > --- /dev/null
> > +++ b/Documentation/ABI/testing/sysfs-driver-dlb
> > @@ -0,0 +1,116 @@
> > +What:		/sys/bus/pci/devices/.../total_resources/num_atomic_inflights
> > +What:		/sys/bus/pci/devices/.../total_resources/num_dir_credits
> > +What:		/sys/bus/pci/devices/.../total_resources/num_dir_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_hist_list_entries
> > +What:		/sys/bus/pci/devices/.../total_resources/num_ldb_credits
> > +What:		/sys/bus/pci/devices/.../total_resources/num_ldb_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_cos0_ldb_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_cos1_ldb_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_cos2_ldb_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_cos3_ldb_ports
> > +What:		/sys/bus/pci/devices/.../total_resources/num_ldb_queues
> > +What:		/sys/bus/pci/devices/.../total_resources/num_sched_domains
> > +Date:		Oct 15, 2021
> > +KernelVersion:	5.15
> > +Contact:	mike.ximing.chen@...el.com
> > +Description:
> > +		The total_resources subdirectory contains read-only files that
> > +		indicate the total number of resources in the device.
> > +
> > +		num_atomic_inflights:  Total number of atomic inflights in the
> > +				       device. Atomic inflights refers to the
> > +				       on-device storage used by the atomic
> > +				       scheduler.
> > +
> > +		num_dir_credits:       Total number of directed credits in the
> > +				       device.
> > +
> > +		num_dir_ports:	       Total number of directed ports (and
> > +				       queues) in the device.
> > +
> > +		num_hist_list_entries: Total number of history list entries in
> > +				       the device.
> > +
> > +		num_ldb_credits:       Total number of load-balanced credits in
> > +				       the device.
> > +
> > +		num_ldb_ports:	       Total number of load-balanced ports in
> > +				       the device.
> > +
> > +		num_cos<M>_ldb_ports:  Total number of load-balanced ports
> > +				       belonging to class-of-service M in the
> > +				       device.
> > +
> > +		num_ldb_queues:	       Total number of load-balanced queues in
> > +				       the device.
> > +
> > +		num_sched_domains:     Total number of scheduling domains in the
> > +				       device.
> > +
> 
> Sysfs is only slightly better than /proc as an API.
> If it is just for testing than debugfs might be better.
> 
Sysfs in our driver is not only for testing. It is used for the system configuration
at run time.

> Could this be done with a real netlink interface?
> Maybe as part of devlink?
Thanks for the suggestion. I will look into some sample implementations of
devlink/netlink. Our current plan is to stay with the configfs interface, and
find ways to resolve issues related to atomic update and resource reset at
tear-down time.

Mike