netdev - Re: [PATCH net-next 5/5] tsnep: Add XDP socket zero-copy TX support

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Date:   Wed, 5 Apr 2023 21:15:53 +0200
From:   Gerhard Engleder <gerhard@...leder-embedded.com>
To:     Maciej Fijalkowski <maciej.fijalkowski@...el.com>
Cc:     netdev@...r.kernel.org, bpf@...r.kernel.org, davem@...emloft.net,
        kuba@...nel.org, edumazet@...gle.com, pabeni@...hat.com,
        bjorn@...nel.org, magnus.karlsson@...el.com,
        jonathan.lemon@...il.com
Subject: Re: [PATCH net-next 5/5] tsnep: Add XDP socket zero-copy TX support

On 04.04.23 00:36, Maciej Fijalkowski wrote:
> On Sun, Apr 02, 2023 at 09:38:38PM +0200, Gerhard Engleder wrote:
>> Send and complete XSK pool frames within TX NAPI context. NAPI context
>> is triggered by ndo_xsk_wakeup.
>>
>> Signed-off-by: Gerhard Engleder <gerhard@...leder-embedded.com>
>> ---
>>   drivers/net/ethernet/engleder/tsnep.h      |   2 +
>>   drivers/net/ethernet/engleder/tsnep_main.c | 131 +++++++++++++++++++--
>>   2 files changed, 123 insertions(+), 10 deletions(-)
>>
> 
> (...)
> 
>> +static void tsnep_xdp_xmit_zc(struct tsnep_tx *tx)
>> +{
>> +	int desc_available = tsnep_tx_desc_available(tx);
>> +	struct xdp_desc xdp_desc;
>> +	bool xmit = false;
>> +
>> +	/* ensure that TX ring is not filled up by XDP, always MAX_SKB_FRAGS
>> +	 * will be available for normal TX path and queue is stopped there if
>> +	 * necessary
>> +	 */
>> +	if (desc_available <= (MAX_SKB_FRAGS + 1))
>> +		return;
>> +	desc_available -= MAX_SKB_FRAGS + 1;
>> +
>> +	while (xsk_tx_peek_desc(tx->xsk_pool, &xdp_desc) && desc_available--) {
> 
> Again, I am curious how batch API usage would improve your perf.

I will try xsk_tx_peek_release_desc_batch().

Thank you for the review!

Gerhard