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[204.195.96.226]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-432bd0dade5sm19530643f8f.9.2026.01.08.16.01.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 08 Jan 2026 16:01:06 -0800 (PST) Date: Thu, 8 Jan 2026 16:00:58 -0800 From: Stephen Hemminger To: Scott Mitchell Cc: dev@dpdk.org, mb@smartsharesystems.com Subject: Re: [PATCH v5] net: optimize raw checksum computation Message-ID: <20260108160058.685cf7a7@phoenix.local> In-Reply-To: References: <20260108061338.27217-1-scott.k.mitch1@gmail.com> <20260108081229.60b095b9@phoenix.local> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org On Thu, 8 Jan 2026 16:19:37 -0500 Scott Mitchell wrote: > On Thu, Jan 8, 2026 at 11:12=E2=80=AFAM Stephen Hemminger > wrote: > > > > On Thu, 8 Jan 2026 01:13:38 -0500 > > scott.k.mitch1@gmail.com wrote: > > =20 > > > +#ifdef RTE_CC_GCC > > > + /* Suppress GCC -Wmaybe-uninitialized false positive. No assemb= ly/runtime impacts. */ > > > + asm volatile("" : "+m" (psd_hdr)); > > > +#endif > > > =20 > > > > Maybe rte_compiler_barrier() will do same thing? =20 >=20 > Agreed it feels like a compiler bug but looking for advice if I'm > missing something :) >=20 > My initial concern with rte_compiler_barrier is its a general barrier > which may have broader impacts on > optimizations and compiled code. Will that be an issue in this case? I > wasn't sure and the approach > in the patch is targeted at a specific variable and assembly from > clang/gcc was the same. I will > introduce a macro to make it cleaner and I can replace it with > rte_compiler_barrier if preferred. Maybe try with -fanalyzer and it might tell you more. I suspect some of the aliasing setting are causing issues. Some drivers are turning on no-strict-aliasing