netdev - Re: [PATCH net 1/4] ice: fix page reuse when PAGE

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Message-ID: <b795aee4-d96e-4e9b-8b07-75e42b91a0cf@intel.com>
Date: Tue, 20 Aug 2024 15:10:29 -0700
From: Jacob Keller <jacob.e.keller@...el.com>
To: Tony Nguyen <anthony.l.nguyen@...el.com>, <davem@...emloft.net>,
	<kuba@...nel.org>, <pabeni@...hat.com>, <edumazet@...gle.com>,
	<netdev@...r.kernel.org>
CC: Maciej Fijalkowski <maciej.fijalkowski@...el.com>, Chandan Kumar Rout
	<chandanx.rout@...el.com>
Subject: Re: [PATCH net 1/4] ice: fix page reuse when PAGE_SIZE is over 8k



On 8/20/2024 2:56 PM, Tony Nguyen wrote:
> From: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> 
> Architectures that have PAGE_SIZE >= 8192 such as arm64 should act the
> same as x86 currently, meaning reuse of a page should only take place
> when no one else is busy with it.
> 
> Do two things independently of underlying PAGE_SIZE:
> - store the page count under ice_rx_buf::pgcnt
> - then act upon its value vs ice_rx_buf::pagecnt_bias when making the
>   decision regarding page reuse
> 
> Fixes: 2b245cb29421 ("ice: Implement transmit and NAPI support")
> Signed-off-by: Maciej Fijalkowski <maciej.fijalkowski@...el.com>
> Tested-by: Chandan Kumar Rout <chandanx.rout@...el.com> (A Contingent Worker at Intel)
> Signed-off-by: Tony Nguyen <anthony.l.nguyen@...el.com>
> ---

Seems reasonable.

Reviewed-by: Jacob Keller <jacob.e.keller@...el.com>

>  drivers/net/ethernet/intel/ice/ice_txrx.c | 12 +++---------
>  1 file changed, 3 insertions(+), 9 deletions(-)
> 
> diff --git a/drivers/net/ethernet/intel/ice/ice_txrx.c b/drivers/net/ethernet/intel/ice/ice_txrx.c
> index 8d25b6981269..50211188c1a7 100644
> --- a/drivers/net/ethernet/intel/ice/ice_txrx.c
> +++ b/drivers/net/ethernet/intel/ice/ice_txrx.c
> @@ -837,16 +837,15 @@ ice_can_reuse_rx_page(struct ice_rx_buf *rx_buf)
>  	if (!dev_page_is_reusable(page))
>  		return false;
>  
> -#if (PAGE_SIZE < 8192)
>  	/* if we are only owner of page we can reuse it */
>  	if (unlikely(rx_buf->pgcnt - pagecnt_bias > 1))
>  		return false;
> -#else
> +#if (PAGE_SIZE >= 8192)

Whats with adding PAGE_SIZE >= 8192 here? Oh. I see you removed the
previous check, so this code only ever executed if page size was large. Ok.

>  #define ICE_LAST_OFFSET \
>  	(SKB_WITH_OVERHEAD(PAGE_SIZE) - ICE_RXBUF_2048)
>  	if (rx_buf->page_offset > ICE_LAST_OFFSET)
>  		return false;
> -#endif /* PAGE_SIZE < 8192) */
> +#endif /* PAGE_SIZE >= 8192) */
>  
>  	/* If we have drained the page fragment pool we need to update
>  	 * the pagecnt_bias and page count so that we fully restock the
> @@ -949,12 +948,7 @@ ice_get_rx_buf(struct ice_rx_ring *rx_ring, const unsigned int size,
>  	struct ice_rx_buf *rx_buf;
>  
>  	rx_buf = &rx_ring->rx_buf[ntc];
> -	rx_buf->pgcnt =
> -#if (PAGE_SIZE < 8192)
> -		page_count(rx_buf->page);
> -#else
> -		0;
> -#endif
> +	rx_buf->pgcnt = page_count(rx_buf->page);

yea, seems weird that if page size is large we would just not track the
count? Yea this new flow makes more sense to me.

>  	prefetchw(rx_buf->page);
>  
>  	if (!size)