linux-kernel - RE: [Intel-wired-lan] [PATCH net-next 1/9] e1000: switch to napi_consume

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Date:   Tue, 28 Dec 2021 00:06:37 +0000
From:   "Brelinski, Tony" <tony.brelinski@...el.com>
To:     "Lobakin, Alexandr" <alexandr.lobakin@...el.com>,
        "intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>
CC:     "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Jakub Kicinski <kuba@...nel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: RE: [Intel-wired-lan] [PATCH net-next 1/9] e1000: switch to
 napi_consume_skb()

> -----Original Message-----
> From: Intel-wired-lan <intel-wired-lan-bounces@...osl.org> On Behalf Of
> Alexander Lobakin
> Sent: Tuesday, November 23, 2021 9:19 AM
> To: intel-wired-lan@...ts.osuosl.org
> Cc: netdev@...r.kernel.org; linux-kernel@...r.kernel.org; Jakub Kicinski
> <kuba@...nel.org>; David S. Miller <davem@...emloft.net>
> Subject: [Intel-wired-lan] [PATCH net-next 1/9] e1000: switch to
> napi_consume_skb()
> 
> In order to take the best from per-cpu NAPI skbuff_head caches and CPU
> cycles, let's switch from dev_kfree_skb_any(), which passes skb back to the
> mm layer, to napi_consume_skb(), which feeds those caches on non-zero
> budget instead (falls back to the former on 0).
> Do the replacement in e1000_unmap_and_free_tx_resource(). There are
> 4 call sites of this function throughout the driver:
>  * e1000_clean_tx_ring(). Slowpath, process context, cleans the
>    whole Tx ring on ifdown. Use budget of 0 here;
>  * e1000_tx_map(). Hotpath, net Tx softirq, unmaps the buffers in
>    case of error. Use 0 as well;
>  * e1000_clean_tx_irq(). Hotpath, NAPI Tx completion polling cycle.
>    As the driver doesn't count completed Tx entries towards the NAPI
>    budget, just use the poll budget of 64 to utilize caches.
> 
> Apart from being a preparation for switching to napi_build_skb(), this is
> useful on its own as well, as napi_consume_skb() flushes skb caches by
> batches of 32 instead of one-at-a-time.
> 
> Signed-off-by: Alexander Lobakin <alexandr.lobakin@...el.com>
> Reviewed-by: Michal Swiatkowski <michal.swiatkowski@...ux.intel.com>
> ---
>  drivers/net/ethernet/intel/e1000/e1000_main.c | 12 +++++++-----
>  1 file changed, 7 insertions(+), 5 deletions(-)

Tested-by: Tony Brelinski <tony.brelinski@...el.com>