netdev - RE: [Intel-wired-lan] [PATCH net-next v2 1/6] ice: do not busy-wait to read GNSS data

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Date:   Thu, 20 Apr 2023 20:59:05 +0000
From:   "Mekala, SunithaX D" <sunithax.d.mekala@...el.com>
To:     mschmidt <mschmidt@...hat.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     Andrew Lunn <andrew@...n.ch>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
        "Kolacinski, Karol" <karol.kolacinski@...el.com>,
        "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
        Simon Horman <simon.horman@...igine.com>
Subject: RE: [Intel-wired-lan] [PATCH net-next v2 1/6] ice: do not busy-wait
 to read GNSS data

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of Michal Schmidt
> Sent: Wednesday, April 12, 2023 1:19 AM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: Andrew Lunn <andrew@...n.ch>; netdev@...r.kernel.org; Brandeburg, Jesse <jesse.brandeburg@...el.com>; Kolacinski, Karol <karol.kolacinski@...el.com>; Nguyen, Anthony L <anthony.l.nguyen@...el.com>; Simon Horman <simon.horman@...igine.com>
> Subject: [Intel-wired-lan] [PATCH net-next v2 1/6] ice: do not busy-wait to read GNSS data
>
> The ice-gnss-<dev_name> kernel thread, which reads data from the u-blox GNSS module, keep a CPU core almost 100% busy. The main reason is that it busy-waits for data to become available.
>
> A simple improvement would be to replace the "mdelay(10);" in
ice_gnss_read() with sleeping. A better fix is to not do any waiting directly in the function and just requeue this delayed work as needed.
The advantage is that canceling the work from ice_gnss_exit() becomes immediate, rather than taking up to ~2.5 seconds (ICE_MAX_UBX_READ_TRIES
* 10 ms).
>
> This lowers the CPU usage of the ice-gnss-<dev_name> thread on my system from ~90 % to ~8 %.
>
> I am not sure if the larger 0.1 s pause after inserting data into the gnss subsystem is really necessary, but I'm keeping that as it was.
> 
> Of course, ideally the driver would not have to poll at all, but I don't know if the E810 can watch for GNSS data availability over the i2c bus by itself and notify the driver.
>
> Signed-off-by: Michal Schmidt <mschmidt@...hat.com>
> ---
> drivers/net/ethernet/intel/ice/ice_gnss.c | 42 ++++++++++-------------  drivers/net/ethernet/intel/ice/ice_gnss.h |  3 +-
> 2 files changed, 20 insertions(+), 25 deletions(-)
>
Tested-by: Sunitha Mekala <sunithax.d.mekala@...el.com> (A Contingent worker at Intel)