Date: Thu, 15 Sep 2011 22:21:27 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: "K. Macy" <kmacy@freebsd.org> Cc: FreeBSD Hackers <freebsd-hackers@freebsd.org>, Arnaud Lacombe <lacombar@gmail.com> Subject: Re: buf_ring(9) API precisions Message-ID: <alpine.BSF.2.00.1109152219380.14815@fledge.watson.org> In-Reply-To: <CAHM0Q_P7NRQXay-ho1E--P4QnV5kr0eTo48NT21dbJjpbmAF=Q@mail.gmail.com> References: <CACqU3MXQ6tD804fKymeFeKDnHndSXVvHJwepYztB4DsnNmtMiw@mail.gmail.com> <CAHM0Q_P7NRQXay-ho1E--P4QnV5kr0eTo48NT21dbJjpbmAF=Q@mail.gmail.com>
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On Thu, 15 Sep 2011, K. Macy wrote: >> Why are you making an MD guess, the amount of padding to fit the size of a >> cache line, in MI API ? Strangely enough, you did not make this assumption >> in, say r205488 (picked randomly). > > It has been several years, and I haven't done any work in svn in over a > year, I don't remember. I probably meant to refine it in a later iteration. > > If you would like to send me a patch addressing this I'd be more than happy > to apply it if appropriate. Otherwise, I will deal with it some time after 9 > settles. > > Thanks for pointing this out. I'm not sure if gcc (and friends) allow __aligned(CACHE_LINE_SIZE) to be used on individual elements of a struct (causing appropriate padding to be added), but that may be one option here. Of course, that introduces a further alignment requirement on the struct itself, so a moderate amount of care would need to be used. Robert
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