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[146.241.59.53]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-43ab155eb77sm22675765e9.32.2025.02.25.03.27.16 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 25 Feb 2025 03:27:17 -0800 (PST) Message-ID: <50019760-440b-4b0c-816f-d262f747a555@redhat.com> Date: Tue, 25 Feb 2025 12:27:15 +0100 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH net-next 1/2] page_pool: Convert page_pool_recycle_stats to u64_stats_t. To: Yunsheng Lin , Sebastian Andrzej Siewior , linux-rdma@vger.kernel.org, netdev@vger.kernel.org Cc: "David S. Miller" , Andrew Lunn , Eric Dumazet , Ilias Apalodimas , Jakub Kicinski , Jesper Dangaard Brouer , Leon Romanovsky , Saeed Mahameed , Simon Horman , Tariq Toukan , Thomas Gleixner References: <20250221115221.291006-1-bigeasy@linutronix.de> <20250221115221.291006-2-bigeasy@linutronix.de> <307939b7-8f51-437a-b5b2-ac5342630504@huawei.com> Content-Language: en-US From: Paolo Abeni In-Reply-To: <307939b7-8f51-437a-b5b2-ac5342630504@huawei.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 2/22/25 9:13 AM, Yunsheng Lin wrote: > On 2025/2/21 19:52, Sebastian Andrzej Siewior wrote: >> @@ -99,11 +106,19 @@ bool page_pool_get_stats(const struct page_pool *pool, >> const struct page_pool_recycle_stats *pcpu = >> per_cpu_ptr(pool->recycle_stats, cpu); >> >> - stats->recycle_stats.cached += pcpu->cached; >> - stats->recycle_stats.cache_full += pcpu->cache_full; >> - stats->recycle_stats.ring += pcpu->ring; >> - stats->recycle_stats.ring_full += pcpu->ring_full; >> - stats->recycle_stats.released_refcnt += pcpu->released_refcnt; >> + do { >> + start = u64_stats_fetch_begin(&pcpu->syncp); >> + u64_stats_add(&stats->recycle_stats.cached, >> + u64_stats_read(&pcpu->cached)); >> + u64_stats_add(&stats->recycle_stats.cache_full, >> + u64_stats_read(&pcpu->cache_full)); >> + u64_stats_add(&stats->recycle_stats.ring, >> + u64_stats_read(&pcpu->ring)); >> + u64_stats_add(&stats->recycle_stats.ring_full, >> + u64_stats_read(&pcpu->ring_full)); >> + u64_stats_add(&stats->recycle_stats.released_refcnt, >> + u64_stats_read(&pcpu->released_refcnt)); > > It seems the above u64_stats_add() may be called more than one time > if the below u64_stats_fetch_retry() returns true, which might mean > the stats is added more than it is needed. > > It seems more correct to me that pool->alloc_stats is read into a > local varible in the while loop and then do the addition outside > the while loop? I also think the above code is incorrect, and local variables to store the read stats are needed. /P