netdev - RE: [Intel-wired-lan] [PATCH iwl-net v2 2/3] ixgbe: xsk: use ixgbe_desc_unused as the budget in ixgbe_xmit

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <IA3PR11MB89869A1D876059D6EBCB64E0E52AA@IA3PR11MB8986.namprd11.prod.outlook.com>
Date: Wed, 13 Aug 2025 11:14:08 +0000
From: "Loktionov, Aleksandr" <aleksandr.loktionov@...el.com>
To: Jason Xing <kerneljasonxing@...il.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "edumazet@...gle.com" <edumazet@...gle.com>,
	"kuba@...nel.org" <kuba@...nel.org>, "pabeni@...hat.com" <pabeni@...hat.com>,
	"horms@...nel.org" <horms@...nel.org>, "andrew+netdev@...n.ch"
	<andrew+netdev@...n.ch>, "Nguyen, Anthony L" <anthony.l.nguyen@...el.com>,
	"Kitszel, Przemyslaw" <przemyslaw.kitszel@...el.com>, "sdf@...ichev.me"
	<sdf@...ichev.me>, "Zaremba, Larysa" <larysa.zaremba@...el.com>,
	"Fijalkowski, Maciej" <maciej.fijalkowski@...el.com>
CC: "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>, Jason Xing
	<kernelxing@...cent.com>
Subject: RE: [Intel-wired-lan] [PATCH iwl-net v2 2/3] ixgbe: xsk: use
 ixgbe_desc_unused as the budget in ixgbe_xmit_zc



> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf
> Of Jason Xing
> Sent: Tuesday, August 12, 2025 9:55 AM
> To: davem@...emloft.net; edumazet@...gle.com; kuba@...nel.org;
> pabeni@...hat.com; horms@...nel.org; andrew+netdev@...n.ch; Nguyen,
> Anthony L <anthony.l.nguyen@...el.com>; Kitszel, Przemyslaw
> <przemyslaw.kitszel@...el.com>; sdf@...ichev.me; Zaremba, Larysa
> <larysa.zaremba@...el.com>; Fijalkowski, Maciej
> <maciej.fijalkowski@...el.com>
> Cc: intel-wired-lan@...ts.osuosl.org; netdev@...r.kernel.org; Jason
> Xing <kernelxing@...cent.com>
> Subject: [Intel-wired-lan] [PATCH iwl-net v2 2/3] ixgbe: xsk: use
> ixgbe_desc_unused as the budget in ixgbe_xmit_zc
> 
> From: Jason Xing <kernelxing@...cent.com>
> 
> - Adjust ixgbe_desc_unused as the budget value.
> - Avoid checking desc_unused over and over again in the loop.
> 
> The patch makes ixgbe follow i40e driver that was done in commit
> 1fd972ebe523 ("i40e: move check of full Tx ring to outside of send
> loop").
> [ Note that the above i40e patch has problem when
> ixgbe_desc_unused(tx_ring)
> returns zero. The zero value as the budget value means we don't have
> any
> possible descs to be sent, so it should return true instead to tell
> the
> napi poll not to launch another poll to handle tx packets. Even
> though
> that patch behaves correctly by returning true in this case, it
> happens
> because of the unexpected underflow of the budget. Taking the
> current
> version of i40e_xmit_zc() as an example, it returns true as
> expected. ]
> Hence, this patch adds a standalone if statement of zero budget in
> front
> of ixgbe_xmit_zc() as explained before.
> 
> Use ixgbe_desc_unused to replace the original fixed budget with the
> number
> of available slots in the Tx ring. It can gain some performance.
You state “It can gain some performance” but provide no numbers
(before/after metrics, hardware, workload, methodology).
The https://www.kernel.org/doc/html/latest/process/submitting-patches.html
ask to quantify optimizations with measurements and discuss trade‑offs.

> 
If the change addresses a behavioral bug (e.g., incorrect NAPI completion behavior when budget is zero),
add Fixes: <sha1> ("commit subject") to help backporting and tracking.

> Signed-off-by: Jason Xing <kernelxing@...cent.com>
> ---
> In this version, I keep it as is (please see the following link)
> https://lore.kernel.org/intel-wired-
> lan/CAL+tcoAUW_J62aw3aGBru+0GmaTjoom1qu8Y=aiSc9EGU09Nww@...l.gmail.c
> om/
> ---
>  drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c | 13 +++++--------
>  1 file changed, 5 insertions(+), 8 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> index a463c5ac9c7c..f3d3f5c1cdc7 100644
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_xsk.c
> @@ -393,17 +393,14 @@ static bool ixgbe_xmit_zc(struct ixgbe_ring
> *xdp_ring, unsigned int budget)
>  	struct xsk_buff_pool *pool = xdp_ring->xsk_pool;
>  	union ixgbe_adv_tx_desc *tx_desc = NULL;
>  	struct ixgbe_tx_buffer *tx_bi;
> -	bool work_done = true;
>  	struct xdp_desc desc;
>  	dma_addr_t dma;
>  	u32 cmd_type;
> 
> -	while (likely(budget)) {
> -		if (unlikely(!ixgbe_desc_unused(xdp_ring))) {
> -			work_done = false;
> -			break;
> -		}
> +	if (!budget)
> +		return true;
> 
> +	while (likely(budget)) {
>  		if (!netif_carrier_ok(xdp_ring->netdev))
>  			break;
> 
> @@ -442,7 +439,7 @@ static bool ixgbe_xmit_zc(struct ixgbe_ring
> *xdp_ring, unsigned int budget)
>  		xsk_tx_release(pool);
>  	}
> 
> -	return !!budget && work_done;
> +	return !!budget;
>  }
> 
>  static void ixgbe_clean_xdp_tx_buffer(struct ixgbe_ring *tx_ring,
> @@ -505,7 +502,7 @@ bool ixgbe_clean_xdp_tx_irq(struct
> ixgbe_q_vector *q_vector,
>  	if (xsk_uses_need_wakeup(pool))
>  		xsk_set_tx_need_wakeup(pool);
> 
> -	return ixgbe_xmit_zc(tx_ring, q_vector->tx.work_limit);
> +	return ixgbe_xmit_zc(tx_ring, ixgbe_desc_unused(tx_ring));
>  }
> 
>  int ixgbe_xsk_wakeup(struct net_device *dev, u32 qid, u32 flags)
> --
> 2.41.3