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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id a640c23a62f3a-b07833ffc38sm188938666b.92.2025.09.10.09.42.19 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 10 Sep 2025 09:42:21 -0700 (PDT) Date: Wed, 10 Sep 2025 09:09:34 -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: <20250910090926.204ff85d@hermes.local> In-Reply-To: <151c401a-87dc-423c-8bae-89d325dc8c90@6wind.com> References: <20250908070414.1297844-1-thierry.herbelot@6wind.com> <20250909054023.3263401-1-thierry.herbelot@6wind.com> <20250909091724.2ea0615e@hermes.local> <151c401a-87dc-423c-8bae-89d325dc8c90@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 Wed, 10 Sep 2025 08:49:38 +0200 Thierry Herbelot wrote: > Hello Stephen, > > On 9/9/25 18:17, Stephen Hemminger wrote: > > 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(); > > } > > > I just checked with this patch, but the error is still present: > > testpmd> show fwd stats all > > ---------------------- Forward statistics for port 0 > ---------------------- > RX-packets: 0 RX-dropped: 10 RX-total: 10 > RX-error: 0 > RX-nombufs: 10 > TX-packets: 0 TX-dropped: 0 TX-total: 0 > > ---------------------------------------------------------------------------- > > The error chain is: > > RX-nombufs > => (testpmd) stats.rx_nombuf > => (qede) p_stats->common.no_buff_discards > => (qede/base) HILO_64_REGPAIR(mstats.no_buff_discard) > (internal to the NIC) > Thanks, lets root cause this (rather than paper it over) because other drivers may have same issue. Since no mbufs are present looks like rx discriptor never made it to NIC