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From: Tal Shnaiderman <>
To: Dmitry Kozlyuk <>,
	Thomas Monjalon <>,
	"" <>,
	"" <>,
	"" <>,
	"" <>,
	"Dmitry Malloy (MESHCHANINOV)" <>,
	Yohad Tor <>
Cc: "" <>
Subject: [dpdk-dev] rte_mbuf structure size in Windows
Date: Wed, 13 May 2020 07:55:07 +0000	[thread overview]
Message-ID: <> (raw)


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? 



             reply	other threads:[~2020-05-13  7:55 UTC|newest]

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