From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mails.dpdk.org (mails.dpdk.org [217.70.189.124]) by inbox.dpdk.org (Postfix) with ESMTP id 5A91043B76; Tue, 5 Mar 2024 18:37:20 +0100 (CET) Received: from mails.dpdk.org (localhost [127.0.0.1]) by mails.dpdk.org (Postfix) with ESMTP id 4584440271; Tue, 5 Mar 2024 18:37:20 +0100 (CET) Received: from linux.microsoft.com (linux.microsoft.com [13.77.154.182]) by mails.dpdk.org (Postfix) with ESMTP id 68DE740270 for ; Tue, 5 Mar 2024 18:37:18 +0100 (CET) Received: by linux.microsoft.com (Postfix, from userid 1086) id B247B20B74C0; Tue, 5 Mar 2024 09:37:17 -0800 (PST) DKIM-Filter: OpenDKIM Filter v2.11.0 linux.microsoft.com B247B20B74C0 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.microsoft.com; s=default; t=1709660237; bh=JdIaE23NX/EtOlQVP1K3TUbZDolfrzl2xDC+2sWQ8/A=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=iOO8HyPnU9j/a4XmtaClDqt5bTln4+JKyrGp7Ozag8L9AxFYXwnz/jfxwaxcwNm4u DMtrU0qBvqGGjk2jQuLla22h35cKssVfJR6AWajEwAnKbOf8NoIEGa4ktfwNGVmHr9 j+C+RKb5gM6W2AmtvufWmcFFcGZxN9MG7Wa8J3tU= Date: Tue, 5 Mar 2024 09:37:17 -0800 From: Tyler Retzlaff To: David Marchand Cc: dev@dpdk.org, Andrew Rybchenko , Bruce Richardson , Chengwen Feng , Cristian Dumitrescu , David Christensen , David Hunt , Ferruh Yigit , Honnappa Nagarahalli , Jasvinder Singh , Jerin Jacob , Kevin Laatz , Konstantin Ananyev , Min Zhou , Ruifeng Wang , Sameh Gobriel , Stanislaw Kardach , Thomas Monjalon , Vladimir Medvedkin , Yipeng Wang Subject: Re: [PATCH v7 08/39] mbuf: use C11 alignas Message-ID: <20240305173717.GA18937@linuxonhyperv3.guj3yctzbm1etfxqx2vob5hsef.xx.internal.cloudapp.net> References: <1707873986-29352-1-git-send-email-roretzla@linux.microsoft.com> <1709574764-9041-1-git-send-email-roretzla@linux.microsoft.com> <1709574764-9041-9-git-send-email-roretzla@linux.microsoft.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) 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 Tue, Mar 05, 2024 at 03:30:49PM +0100, David Marchand wrote: > On Mon, Mar 4, 2024 at 6:54 PM Tyler Retzlaff > wrote: > > > > The current location used for __rte_aligned(a) for alignment of types > > and variables is not compatible with MSVC. There is only a single > > location accepted by both toolchains. > > > > For variables standard C11 offers alignas(a) supported by conformant > > compilers i.e. both MSVC and GCC. > > > > For types the standard offers no alignment facility that compatibly > > interoperates with C and C++ but may be achieved by relocating the > > placement of __rte_aligned(a) to the aforementioned location accepted > > by all currently supported toolchains. > > > > To allow alignment for both compilers do the following: > > > > * Move __rte_aligned from the end of {struct,union} definitions to > > be between {struct,union} and tag. > > > > The placement between {struct,union} and the tag allows the desired > > alignment to be imparted on the type regardless of the toolchain being > > used for all of GCC, LLVM, MSVC compilers building both C and C++. > > > > * Replace use of __rte_aligned(a) on variables/fields with alignas(a). > > > > Signed-off-by: Tyler Retzlaff > > Acked-by: Morten Brørup > > Acked-by: Konstantin Ananyev > > --- > > lib/mbuf/rte_mbuf_core.h | 6 +++--- > > 1 file changed, 3 insertions(+), 3 deletions(-) > > > > diff --git a/lib/mbuf/rte_mbuf_core.h b/lib/mbuf/rte_mbuf_core.h > > index 5688683..917a811 100644 > > --- a/lib/mbuf/rte_mbuf_core.h > > +++ b/lib/mbuf/rte_mbuf_core.h > > @@ -463,7 +463,7 @@ enum { > > /** > > * The generic rte_mbuf, containing a packet mbuf. > > */ > > -struct rte_mbuf { > > +struct __rte_cache_aligned rte_mbuf { > > RTE_MARKER cacheline0; > > > > void *buf_addr; /**< Virtual address of segment buffer. */ > > @@ -476,7 +476,7 @@ struct rte_mbuf { > > * same mbuf cacheline0 layout for 32-bit and 64-bit. This makes > > * working on vector drivers easier. > > */ > > - rte_iova_t buf_iova __rte_aligned(sizeof(rte_iova_t)); > > + alignas(sizeof(rte_iova_t)) rte_iova_t buf_iova; > > #else > > /** > > * Next segment of scattered packet. > > @@ -662,7 +662,7 @@ struct rte_mbuf { > > uint16_t timesync; > > > > uint32_t dynfield1[9]; /**< Reserved for dynamic fields. */ > > -} __rte_cache_aligned; > > +}; > > I probably missed the discussion, but why is cacheline1 not handled in > this patch? > I was expecting a: > - RTE_MARKER cacheline1 __rte_cache_min_aligned; > + alignas(RTE_CACHE_LINE_MIN_SIZE) RTE_MARKER cacheline1; I should have replaced it I just missed it. Could I get you to fix it up? We have 2 options. 1. You can leave it as is, eventually the other series I have dealing with the markers I will probably remove the cacheline1 marker anyway. 2. You could adjust it as you've identified above, just move alignas before the field type and name. If you want me to submit a v8 for this let me know I'll do it right away. Thanks! > > > -- > David Marchand