linux-kernel - RE: [Intel-wired-lan] [PATCH iwl-next v5 03/13] idpf: use a saner limit for default number of queues to allocate

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Message-ID: <DM4PR11MB64556AAED5AC02461285ECEE9800A@DM4PR11MB6455.namprd11.prod.outlook.com>
Date: Thu, 4 Sep 2025 16:42:11 +0000
From: "R, Ramu" <ramu.r@...el.com>
To: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC: "Lobakin, Aleksander" <aleksander.lobakin@...el.com>, "Kubiak, Michal"
	<michal.kubiak@...el.com>, "Fijalkowski, Maciej"
	<maciej.fijalkowski@...el.com>, "Nguyen, Anthony L"
	<anthony.l.nguyen@...el.com>, "Kitszel, Przemyslaw"
	<przemyslaw.kitszel@...el.com>, Andrew Lunn <andrew+netdev@...n.ch>, "David
 S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, "Jakub
 Kicinski" <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, "Alexei
 Starovoitov" <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, "Simon
 Horman" <horms@...nel.org>, NXNE CNSE OSDT ITP Upstreaming
	<nxne.cnse.osdt.itp.upstreaming@...el.com>, "bpf@...r.kernel.org"
	<bpf@...r.kernel.org>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [Intel-wired-lan] [PATCH iwl-next v5 03/13] idpf: use a saner
 limit for default number of queues to allocate

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of
> Alexander Lobakin
> Sent: Tuesday, August 26, 2025 9:25 PM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: Lobakin, Aleksander <aleksander.lobakin@...el.com>; Kubiak, Michal
> <michal.kubiak@...el.com>; Fijalkowski, Maciej
> <maciej.fijalkowski@...el.com>; Nguyen, Anthony L
> <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@...el.com>; Andrew Lunn <andrew+netdev@...n.ch>;
> David S. Miller <davem@...emloft.net>; Eric Dumazet
> <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; Alexei Starovoitov <ast@...nel.org>; Daniel
> Borkmann <daniel@...earbox.net>; Simon Horman <horms@...nel.org>;
> NXNE CNSE OSDT ITP Upstreaming
> <nxne.cnse.osdt.itp.upstreaming@...el.com>; bpf@...r.kernel.org;
> netdev@...r.kernel.org; linux-kernel@...r.kernel.org
> Subject: [Intel-wired-lan] [PATCH iwl-next v5 03/13] idpf: use a saner limit for
> default number of queues to allocate
> 
> Currently, the maximum number of queues available for one vport is 16.
> This is hardcoded, but then the function calculating the optimal number of
> queues takes min(16, num_online_cpus()).
> In order to be able to allocate more queues, which will be then used for XDP,
> stop hardcoding 16 and rely on what the device gives us[*]. Instead of
> num_online_cpus(), which is considered suboptimal since at least 2013, use
> netif_get_num_default_rss_queues() to still have free queues in the pool.
> 
> [*] With the note:
> 
> Currently, idpf always allocates `IDPF_MAX_BUFQS_PER_RXQ_GRP` (== 2)
> buffer queues for each Rx queue and one completion queue for each Tx for
> best performance. But there was no check whether such number is availabe,
> IOW the assumption was not backed by any "harmonizing" / actual checks.
> Fix this while at it.
> 
> nr_cpu_ids number of Tx queues are needed only for lockless XDP sending,
> the regular stack doesn't benefit from that anyhow.
> On a 128-thread Xeon, this now gives me 32 regular Tx queues and leaves
> 224 free for XDP (128 of which will handle XDP_TX, .ndo_xdp_xmit(), and XSk
> xmit when enabled).
> 
> Note 2:
> 
> Unfortunately, some CP/FW versions are not able to
> reconfigure/enable/disable large amount of queues within the minimum
> timeout (2 seconds). For now, fall back to the default timeout for every
> operation until this is resolved.
> 
> Signed-off-by: Alexander Lobakin <aleksander.lobakin@...el.com>
> ---
>  .../net/ethernet/intel/idpf/idpf_virtchnl.h   |  1 -
>  drivers/net/ethernet/intel/idpf/idpf_txrx.c   |  8 +--
>  .../net/ethernet/intel/idpf/idpf_virtchnl.c   | 62 +++++++++++--------
>  3 files changed, 38 insertions(+), 33 deletions(-)
> 
Tested-by: R,Ramu <ramu.r@...el.com>