netdev - Re: [PATCH net-next v3 3/4] page_pool: Convert page_pool_recycle_stats to u64_stats

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Message-ID: <988c920b-56b8-43f6-a42c-54e3ea6dc261@huawei.com>
Date: Tue, 8 Apr 2025 20:13:09 +0800
From: Yunsheng Lin <linyunsheng@...wei.com>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
	<linux-rdma@...r.kernel.org>, <linux-rt-devel@...ts.linux.dev>,
	<netdev@...r.kernel.org>
CC: "David S. Miller" <davem@...emloft.net>, Andrew Lunn
	<andrew+netdev@...n.ch>, Eric Dumazet <edumazet@...gle.com>, Ilias Apalodimas
	<ilias.apalodimas@...aro.org>, Jakub Kicinski <kuba@...nel.org>, Jesper
 Dangaard Brouer <hawk@...nel.org>, Joe Damato <jdamato@...tly.com>, Leon
 Romanovsky <leon@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Saeed Mahameed
	<saeedm@...dia.com>, Simon Horman <horms@...nel.org>, Tariq Toukan
	<tariqt@...dia.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH net-next v3 3/4] page_pool: Convert
 page_pool_recycle_stats to u64_stats_t.

On 2025/4/8 18:59, Sebastian Andrzej Siewior wrote:
> Using u64 for statistics can lead to inconsistency on 32bit because an
> update and a read requires to access two 32bit values.
> This can be avoided by using u64_stats_t for the counters and
> u64_stats_sync for the required synchronisation on 32bit platforms. The
> synchronisation is a NOP on 64bit architectures.
> 
> Use u64_stats_t for the counters in page_pool_recycle_stats.
> Add U64_STATS_ZERO, a static initializer for u64_stats_t.
> 
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
>  Documentation/networking/page_pool.rst |  6 +--
>  include/linux/u64_stats_sync.h         |  5 +++
>  include/net/page_pool/types.h          | 13 ++++---
>  net/core/page_pool.c                   | 52 ++++++++++++++++++--------
>  net/core/page_pool_user.c              | 10 ++---
>  5 files changed, 58 insertions(+), 28 deletions(-)
> 
> diff --git a/Documentation/networking/page_pool.rst b/Documentation/networking/page_pool.rst
> index 9d958128a57cb..5215fd51a334a 100644
> --- a/Documentation/networking/page_pool.rst
> +++ b/Documentation/networking/page_pool.rst
> @@ -181,11 +181,11 @@ Stats
>  
>  	#ifdef CONFIG_PAGE_POOL_STATS
>  	/* retrieve stats */
> -	struct page_pool_stats stats = { 0 };
> +	struct page_pool_stats stats = { };
>  	if (page_pool_get_stats(page_pool, &stats)) {
>  		/* perhaps the driver reports statistics with ethool */
> -		ethtool_print_allocation_stats(&stats.alloc_stats);
> -		ethtool_print_recycle_stats(&stats.recycle_stats);
> +		ethtool_print_allocation_stats(u64_stats_read(&stats.alloc_stats));
> +		ethtool_print_recycle_stats(u64_stats_read(&stats.recycle_stats));

The above seems like an unnecessary change? as stats.alloc_stats and
stats.recycle_stats are not really 'u64_stats_t' type.

Otherwise, LGTM.
Reviewed-by: Yunsheng Lin <linyunsheng@...wei.com>