Date: Wed, 31 Oct 2012 11:50:17 -0700 From: Adrian Chadd <adrian@freebsd.org> To: attilio@freebsd.org Cc: svn-src-head@freebsd.org, Ian Lepore <freebsd@damnhippie.dyndns.org>, svn-src-all@freebsd.org, src-committers@freebsd.org Subject: Re: svn commit: r242402 - in head/sys: kern vm Message-ID: <CAJ-VmokqEFX4wQYh-ojo3kcWUPj5L-V_k0Nj-u3sQByVypkDFw@mail.gmail.com> In-Reply-To: <CAJ-FndC7QwpNAjzQTumqTY6Sj_RszXPwc0pbHv2-pRGMqbw0ww@mail.gmail.com> References: <201210311807.q9VI7IcX000993@svn.freebsd.org> <CAJ-FndDRkBS57e9mzZoJWX5ugJ0KBGxhMSO50KB8Wm8MFudjCA@mail.gmail.com> <1351707964.1120.97.camel@revolution.hippie.lan> <CAJ-FndC7QwpNAjzQTumqTY6Sj_RszXPwc0pbHv2-pRGMqbw0ww@mail.gmail.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On 31 October 2012 11:33, Attilio Rao <attilio@freebsd.org> wrote: >> Doesn't this padding to cache line size only help x86 processors in an >> SMP kernel? I was expecting to see some #ifdef SMP so that we don't pay >> a big price for no gain in small-memory ARM systems and such. But maybe >> I'm misunderstanding the reason for the padding. > > I didn't want to do this because this would be meaning that SMP option > may become a completely killer for modules/kernel ABI compatibility. Right, but you didn't make it configurable for us embedded peeps who still care about memory usage. > Also, if you look at the modified list of locks I don't think they > should be too much, I hardly believe ARM UP is going to hurt that much > from loosing some padding in tdq structures or callout. There's a few million more embedded MIPS boards out there with 16mb/32mb of RAM than target PCs for FreeBSD. Would you mind making the padding part configurable and just default it to "do the padding" ? That way for the atheros MIPS builds I can turn it off and save on the memory overhead. Thanks, Adrian
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?CAJ-VmokqEFX4wQYh-ojo3kcWUPj5L-V_k0Nj-u3sQByVypkDFw>