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charset="us-ascii" Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-AuthSource: DM4PR12MB7549.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-Network-Message-Id: 817f3663-819c-4571-3b5e-08dcf8bb3965 X-MS-Exchange-CrossTenant-originalarrivaltime: 30 Oct 2024 08:16:58.4745 (UTC) X-MS-Exchange-CrossTenant-fromentityheader: Hosted X-MS-Exchange-CrossTenant-id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-mailboxtype: HOSTED X-MS-Exchange-CrossTenant-userprincipalname: XqHwrLIp22PAkWueMsHu20WtU7kRP2S93FANn7erDRAx7xm/mv5Pvy7qlr4KE9UMo1OtfurwaHZ9GoxPQh99gg== X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM4PR12MB6566 X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Hi, > -----Original Message----- > From: Stephen Hemminger > Sent: Tuesday, October 29, 2024 6:07 PM > To: Minggang(Gavin) Li > Cc: Slava Ovsiienko ; Matan Azrad > ; Ori Kam ; NBU-Contact-Thomas > Monjalon (EXTERNAL) ; Dariusz Sosnowski > ; Bing Zhao ; Suanming Mou > ; dev@dpdk.org; Raslan Darawsheh > ; rongwei liu > Subject: Re: [PATCH V2 3/7] net/mlx5: add new devargs to control probe > optimization >=20 > On Tue, 29 Oct 2024 16:27:25 +0800 > "Minggang(Gavin) Li" wrote: >=20 > > On 10/28/2024 11:47 PM, Stephen Hemminger wrote: > > > On Mon, 28 Oct 2024 11:18:18 +0200 > > > "Minggang Li(Gavin)" wrote: > > > > > >> +- ``probe_opt_en`` parameter [int] > > >> + > > >> + A non-zero value optimizes the probe process, especially for larg= e > scale. > > >> + PMD will hold the IB device information internally and reuse it. > > >> + > > >> + By default, the PMD will set this value to 0. > > >> + > > > Is there ever a case where this should not be used? > > > > > > It would be better to just detect and use it if available. > > > This driver does not need more options... > > The new mechanism, which is required by few users, so we would not > > break production and with the option we encourage to use new way only > > those who actually needs. Once we see the new way is reliable - we > > will change the default value. >=20 > I understand that philosophy but it leads to a maze of technical debt. This specific case is not about philosophy in general. We have users with huge number of SFs/VFs configured and experiencing the i= ssues with gigantic probing timings (literally - tens of minutes). This story was= lasting long time, we were trying different approaches, then admitted we had to upd= ate kernel, etc., and eventually we had things done and it resulted in this series. The new approach is event driven and based on the handling the new kernel-g= enerated events. So, it relies on system-wide environment and might be problematic on some h= osts (we do not expect too much though). At the same time, the existing probe approach provides acceptable performan= ce and satisfies the vast majority of the users. So, our main objective is not to= break anything in production (most users), the second objective - to resolve issues of som= e users with configuration specifics (few users). That's why we would prefer to have the= devarg (with all its cons and pros) and set the devarg default value to false. Lat= er, once the new kernel API spreads and we have good production statistics we can consider altering= the default value to true or obsolete the devarg at all. Does this approach look reason= able? > Has a full suite of tests been done with both settings of the option? > Has both values been tested on all combinations of platforms and OS > releases? We cannot keep the new approach only - we have to maintain legacy kernel co= mpatibility. So - there always will be 2 branches of tests, till legacy kernels retireme= nt. And having the devarg might even simplify the testing - the single host can be used for both runs= , with different devargs values. > My point is every option adds to the necessary test matrix geometrically! Once we added the new probing mechanics - the test matrix is ALREADY extend= ed , regardless of devargs implementation. The devarg just makes our users livings in fields easier. With best regards, Slava