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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45dda4f2a0dsm191559295e9.2.2025.09.09.09.17.29 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 09 Sep 2025 09:17:31 -0700 (PDT) Date: Tue, 9 Sep 2025 09:17:24 -0700 From: Stephen Hemminger To: Thierry Herbelot Cc: dev@dpdk.org, Thomas Monjalon , Devendra Singh Rawat , Alok Prasad , Jerin Jacob , Olivier Matz , Edwin Brossette , stable@dpdk.org Subject: Re: [V3] net/qede: reduce the optimization level for gcc > 11 Message-ID: <20250909091724.2ea0615e@hermes.local> In-Reply-To: <20250909054023.3263401-1-thierry.herbelot@6wind.com> References: <20250908070414.1297844-1-thierry.herbelot@6wind.com> <20250909054023.3263401-1-thierry.herbelot@6wind.com> MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org On Tue, 9 Sep 2025 07:40:23 +0200 Thierry Herbelot wrote: > The qede PMD stopped working under Ubuntu-24.04 (using gcc-13) when > compiled with -O3 (default level for all DPDK code). A bug is opened > for this issue (see Link). The same issue is also seen with gcc-12 > and gcc-14. The issue is not seen with clang-20. > > A first workaround is to just disable all optimizations (-O0), which > restores packet Rx with Qlogic NICs. However, the performance impact > is not acceptable (around 50% drop). > > A better compromise is to use -O1 for the qede PMD: > - there is some perf impact, > - but the PMD is working as expected (packets are correctly received). > > When compiling with both -O2 and -O3 and gcc > 11, there is no packet > reception when using the qede PMD. The root cause could be missing > 'volatile' keywords or missing memory barriers in the qede PMD code. > > Link: https://bugs.dpdk.org/show_bug.cgi?id=1379 > Signed-off-by: Thierry Herbelot Which rx_burst gets used on that hardware? Is there any indication of errors (like rx_mbuf_alloc_failed) in the stats. The driver does not appear to have any write barrier after updating the consumed packets. Would this help? diff --git a/drivers/net/qede/qede_rxtx.c b/drivers/net/qede/qede_rxtx.c index 25e28fd9f6..1b5109d966 100644 --- a/drivers/net/qede/qede_rxtx.c +++ b/drivers/net/qede/qede_rxtx.c @@ -1295,6 +1295,8 @@ static inline void qede_rx_bd_ring_consume(struct qede_rx_queue *rxq) { ecore_chain_consume(&rxq->rx_bd_ring); rxq->sw_rx_cons++; + + rte_wmb(); }