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From: Tal Shnaiderman <talshn@mellanox.com>
To: Omar Cardona <ocardona@microsoft.com>,
	Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>,
	Thomas Monjalon <thomas@monjalon.net>,
	"pallavi.kadam@intel.com" <pallavi.kadam@intel.com>,
	"navasile@linux.microsoft.com" <navasile@linux.microsoft.com>,
	"ranjit.menon@intel.com" <ranjit.menon@intel.com>,
	Harini Ramakrishnan <Harini.Ramakrishnan@microsoft.com>,
	"Dmitry Malloy (MESHCHANINOV)" <dmitrym@microsoft.com>,
	Yohad Tor <yohadt@mellanox.com>, Jie Zhou <jizh@microsoft.com>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] rte_mbuf structure size in Windows
Date: Wed, 13 May 2020 08:50:18 +0000	[thread overview]
Message-ID: <AM0PR05MB5313629FE6EBB912A5C05F46A9BF0@AM0PR05MB5313.eurprd05.prod.outlook.com> (raw)
In-Reply-To: <CY4PR21MB0277F15AEA6DDB452D0A38B8DABF0@CY4PR21MB0277.namprd21.prod.outlook.com>

Thank you Omar, this is indeed the same issue.

> -----Original Message-----
> From: Omar Cardona <ocardona@microsoft.com>
> Sent: Wednesday, May 13, 2020 11:08 AM
> To: Tal Shnaiderman <talshn@mellanox.com>; Dmitry Kozlyuk
> <dmitry.kozliuk@gmail.com>; Thomas Monjalon <thomas@monjalon.net>;
> pallavi.kadam@intel.com; navasile@linux.microsoft.com;
> ranjit.menon@intel.com; Harini Ramakrishnan
> <Harini.Ramakrishnan@microsoft.com>; Dmitry Malloy (MESHCHANINOV)
> <dmitrym@microsoft.com>; Yohad Tor <yohadt@mellanox.com>; Jie Zhou
> <jizh@microsoft.com>
> Cc: dev@dpdk.org
> Subject: RE: rte_mbuf structure size in Windows
> 
> Tal,
> See attached compiler bug section for details.
> 
> -----Original Message-----
> From: Omar Cardona
> Sent: Wednesday, May 13, 2020 1:04 AM
> To: Tal Shnaiderman <talshn@mellanox.com>; Dmitry Kozlyuk
> <dmitry.kozliuk@gmail.com>; Thomas Monjalon <thomas@monjalon.net>;
> pallavi.kadam@intel.com; navasile@linux.microsoft.com;
> ranjit.menon@intel.com; Harini Ramakrishnan
> <Harini.Ramakrishnan@microsoft.com>; Dmitry Malloy (MESHCHANINOV)
> <dmitrym@microsoft.com>; Yohad Tor <yohadt@mellanox.com>; Jie Zhou
> <jizh@microsoft.com>
> Cc: dev@dpdk.org
> Subject: RE: rte_mbuf structure size in Windows
> 
> IIRC, it's this issue.
> https://eur03.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbugs.
> llvm.org%2Fshow_bug.cgi%3Fid%3D24383&amp;data=02%7C01%7Ctalshn%4
> 0mellanox.com%7C2987047b646b4854350e08d7f714b2ea%7Ca652971c7d2e4
> d9ba6a4d149256f461b%7C0%7C0%7C637249540596603575&amp;sdata=83m
> NExOvXtXpKIt%2FZaqkoZadkuGpX1olQE3Scc1xOAQ%3D&amp;reserved=0
> 
> -----Original Message-----
> From: Tal Shnaiderman <talshn@mellanox.com>
> Sent: Wednesday, May 13, 2020 12:55 AM
> To: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>; Thomas Monjalon
> <thomas@monjalon.net>; pallavi.kadam@intel.com;
> navasile@linux.microsoft.com; ranjit.menon@intel.com; Harini
> Ramakrishnan <Harini.Ramakrishnan@microsoft.com>; Omar Cardona
> <ocardona@microsoft.com>; Dmitry Malloy (MESHCHANINOV)
> <dmitrym@microsoft.com>; Yohad Tor <yohadt@mellanox.com>
> Cc: dev@dpdk.org
> Subject: [EXTERNAL] rte_mbuf structure size in Windows
> 
> Hi,
> 
> I've noticed that there is a difference between the size of rte_mbuf in a Unix
> build comparing to Windows.
> 
> The requirements is for rte_mbuf is to be RTE_CACHE_LINE_MIN_SIZE * 2
> bytes however when I'm building it in Windows the size is
> RTE_CACHE_LINE_MIN_SIZE * 3.
> 
> Looks like the diff results from the usage of bit fields inside rte_mbuf, from
> my testing it looks to me like the usage of 2 different bit fielded types inside
> rte_mbuf causes additional padding in Windows.
> 
> For example from rte_mbuf, the following unions have the same size in
> Windows and Linux:
> 
> 	union {
> 		uint32_t packet_type;
> 		// bit fields of type uint32_t will follow
> 		...
> 	};...
> 
> 4 bytes both in Unix and Windows.
> 
> 	union {
> 		uint64_t tx_offload;
> 		// bit fields of type uint64_t will follow
> 		...
> 	};
> 
> 8 bytes both in Unix and Windows.
> 
> However when creating a struct containing both unions I'm getting sizeof 16
> bytes in Unix and 24 bytes in Windows.
> 
> Did someone faced this issue before? Is this a result of different alignment
> between gcc and clang when bit fields are used?
> 
> Thanks,
> 
> Tal

  reply	other threads:[~2020-05-13  8:50 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-13  7:55 [dpdk-dev] rte_mbuf structure size in Windows Tal Shnaiderman
2020-05-13  8:04 ` Omar Cardona
2020-05-13  8:07   ` Omar Cardona
2020-05-13  8:50     ` Tal Shnaiderman [this message]
2020-05-13  8:35 ` Dmitry Kozlyuk
2020-05-13  8:55   ` Tal Shnaiderman
2020-05-13  9:34     ` Dmitry Kozlyuk

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