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Date: Mon, 05 May 2014 04:15:57 -0700 From: Hannes Frederic Sowa <hannes@...essinduktion.org> To: Lorenzo Colitti <lorenzo@...gle.com>, netdev@...r.kernel.org Cc: davem@...emloft.net, yoshifuji@...ux-ipv6.org, david.laight@...lab.com, eric.dumazet@...il.com Subject: Re: [PATCH v6 1/2] net: ipv6: Unduplicate UDP, raw, and L2TP sendmsg Hi! On Fri, May 2, 2014, at 12:11, Lorenzo Colitti wrote: > + > +struct ip6_output_opts { > + int hlimit: 9; > + int tclass: 9; > + int dontfrag: 2; > + unsigned connected: 1; > + struct ipv6_txoptions *opt; > +}; I don't think the bitfields are useful, they can cause more RMW cycles and at least on 64-bit systems the structure does not shrink in size if you instead just use s16 and bool types because of the padding needed for the pointer. On 32-bit it does save 4 bytes on the stack, but I don't think it is worth it. If you put the pointer above the other members, newly added fields at the bottom can eat into padding space instead of leaving padding holes in it. Greetings, Hannes -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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