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Message-ID: <d012a523-816b-48af-91c0-4a11f85d592b@huawei.com>
Date: Tue, 8 Apr 2025 20:27:02 +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 4/4] page_pool: Convert page_pool_alloc_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_alloc_stats.
It seems a little overkill for page_pool_alloc_stats as there is only
one updater ensured by NAPI context, but I am not able to think of a better
way, so:
Reviewed-by: Yunsheng Lin <linyunsheng@...wei.com>
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
> ---
> include/net/page_pool/types.h | 14 ++++++-----
> net/core/page_pool.c | 47 +++++++++++++++++++++++++----------
> net/core/page_pool_user.c | 12 ++++-----
> 3 files changed, 48 insertions(+), 25 deletions(-)
>
> diff --git a/include/net/page_pool/types.h b/include/net/page_pool/types.h
> index 54c79a020b334..9406fa69232ee 100644
> --- a/include/net/page_pool/types.h
> +++ b/include/net/page_pool/types.h
> @@ -96,6 +96,7 @@ struct page_pool_params {
> #ifdef CONFIG_PAGE_POOL_STATS
> /**
> * struct page_pool_alloc_stats - allocation statistics
> + * @syncp: synchronisations point for updates.
> * @fast: successful fast path allocations
> * @slow: slow path order-0 allocations
> * @slow_high_order: slow path high order allocations
> @@ -105,12 +106,13 @@ struct page_pool_params {
> * the cache due to a NUMA mismatch
> */
> struct page_pool_alloc_stats {
> - u64 fast;
> - u64 slow;
> - u64 slow_high_order;
> - u64 empty;
> - u64 refill;
> - u64 waive;
> + struct u64_stats_sync syncp;
> + u64_stats_t fast;
> + u64_stats_t slow;
> + u64_stats_t slow_high_order;
> + u64_stats_t empty;
> + u64_stats_t refill;
> + u64_stats_t waive;
> };
>
> /**
> diff --git a/net/core/page_pool.c b/net/core/page_pool.c
> index eb2f5b995022f..46e3c56b76692 100644
> --- a/net/core/page_pool.c
> +++ b/net/core/page_pool.c
> @@ -45,7 +45,14 @@ static DEFINE_PER_CPU(struct page_pool_recycle_stats, pp_system_recycle_stats) =
> };
>
> /* alloc_stat_inc is intended to be used in softirq context */
> -#define alloc_stat_inc(pool, __stat) (pool->alloc_stats.__stat++)
> +#define alloc_stat_inc(pool, __stat) \
> + do { \
> + struct page_pool_alloc_stats *s = &pool->alloc_stats; \
> + u64_stats_update_begin(&s->syncp); \
> + u64_stats_inc(&s->__stat); \
> + u64_stats_update_end(&s->syncp); \
> + } while (0)
> +
> /* recycle_stat_inc is safe to use when preemption is possible. */
> #define recycle_stat_inc(pool, __stat) \
> do { \
> @@ -91,19 +98,32 @@ static const char pp_stats[][ETH_GSTRING_LEN] = {
> bool page_pool_get_stats(const struct page_pool *pool,
> struct page_pool_stats *stats)
> {
> + u64 fast, slow, slow_high_order, empty, refill, waive;
> + const struct page_pool_alloc_stats *alloc_stats;
> unsigned int start;
> int cpu = 0;
>
> if (!stats)
> return false;
>
> + alloc_stats = &pool->alloc_stats;
> /* The caller is responsible to initialize stats. */
> - stats->alloc_stats.fast += pool->alloc_stats.fast;
> - stats->alloc_stats.slow += pool->alloc_stats.slow;
> - stats->alloc_stats.slow_high_order += pool->alloc_stats.slow_high_order;
> - stats->alloc_stats.empty += pool->alloc_stats.empty;
> - stats->alloc_stats.refill += pool->alloc_stats.refill;
> - stats->alloc_stats.waive += pool->alloc_stats.waive;
> + do {
> + start = u64_stats_fetch_begin(&alloc_stats->syncp);
> + fast = u64_stats_read(&alloc_stats->fast);
> + slow = u64_stats_read(&alloc_stats->slow);
> + slow_high_order = u64_stats_read(&alloc_stats->slow_high_order);
> + empty = u64_stats_read(&alloc_stats->empty);
> + refill = u64_stats_read(&alloc_stats->refill);
> + waive = u64_stats_read(&alloc_stats->waive);
> + } while (u64_stats_fetch_retry(&alloc_stats->syncp, start));
> +
> + u64_stats_add(&stats->alloc_stats.fast, fast);
> + u64_stats_add(&stats->alloc_stats.slow, slow);
> + u64_stats_add(&stats->alloc_stats.slow_high_order, slow_high_order);
> + u64_stats_add(&stats->alloc_stats.empty, empty);
> + u64_stats_add(&stats->alloc_stats.refill, refill);
> + u64_stats_add(&stats->alloc_stats.waive, waive);
>
> for_each_possible_cpu(cpu) {
> u64 cached, cache_full, ring, ring_full, released_refcnt;
> @@ -153,12 +173,12 @@ u64 *page_pool_ethtool_stats_get(u64 *data, const void *stats)
> {
> const struct page_pool_stats *pool_stats = stats;
>
> - *data++ = pool_stats->alloc_stats.fast;
> - *data++ = pool_stats->alloc_stats.slow;
> - *data++ = pool_stats->alloc_stats.slow_high_order;
> - *data++ = pool_stats->alloc_stats.empty;
> - *data++ = pool_stats->alloc_stats.refill;
> - *data++ = pool_stats->alloc_stats.waive;
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.fast);
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.slow);
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.slow_high_order);
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.empty);
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.refill);
> + *data++ = u64_stats_read(&pool_stats->alloc_stats.waive);
> *data++ = u64_stats_read(&pool_stats->recycle_stats.cached);
> *data++ = u64_stats_read(&pool_stats->recycle_stats.cache_full);
> *data++ = u64_stats_read(&pool_stats->recycle_stats.ring);
> @@ -283,6 +303,7 @@ static int page_pool_init(struct page_pool *pool,
> pool->recycle_stats = &pp_system_recycle_stats;
> pool->system = true;
> }
> + u64_stats_init(&pool->alloc_stats.syncp);
> #endif
>
> if (ptr_ring_init(&pool->ring, ring_qsize, GFP_KERNEL) < 0) {
> diff --git a/net/core/page_pool_user.c b/net/core/page_pool_user.c
> index 86c22461b7fed..53c1ebe7cbe6b 100644
> --- a/net/core/page_pool_user.c
> +++ b/net/core/page_pool_user.c
> @@ -137,17 +137,17 @@ page_pool_nl_stats_fill(struct sk_buff *rsp, const struct page_pool *pool,
> nla_nest_end(rsp, nest);
>
> if (nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_FAST,
> - stats.alloc_stats.fast) ||
> + u64_stats_read(&stats.alloc_stats.fast)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_SLOW,
> - stats.alloc_stats.slow) ||
> + u64_stats_read(&stats.alloc_stats.slow)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_SLOW_HIGH_ORDER,
> - stats.alloc_stats.slow_high_order) ||
> + u64_stats_read(&stats.alloc_stats.slow_high_order)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_EMPTY,
> - stats.alloc_stats.empty) ||
> + u64_stats_read(&stats.alloc_stats.empty)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_REFILL,
> - stats.alloc_stats.refill) ||
> + u64_stats_read(&stats.alloc_stats.refill)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_ALLOC_WAIVE,
> - stats.alloc_stats.waive) ||
> + u64_stats_read(&stats.alloc_stats.waive)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_RECYCLE_CACHED,
> u64_stats_read(&stats.recycle_stats.cached)) ||
> nla_put_uint(rsp, NETDEV_A_PAGE_POOL_STATS_RECYCLE_CACHE_FULL,
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