Date: Thu, 5 Jul 2018 17:20:32 -0700 From: John Baldwin <jhb@FreeBSD.org> To: Eugene Grosbein <eugen@grosbein.net>, Konstantin Belousov <kostikbel@gmail.com> Cc: Matt Macy <mmacy@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r335916 - head/sys/conf Message-ID: <b89ad5e7-9b65-54d8-652c-5ed3315cd108@FreeBSD.org> In-Reply-To: <5B3EB443.50004@grosbein.net> References: <201807032305.w63N5guY063293@repo.freebsd.org> <20180704142233.GB5562@kib.kiev.ua> <6e5bc5e4-052c-877f-1c36-c72e276ff045@FreeBSD.org> <20180705155417.GI5562@kib.kiev.ua> <2a5b1c50-0f50-bbe1-4fcd-b98f61d24571@FreeBSD.org> <5B3EA725.4010202@grosbein.net> <1dd03d43-6f0d-580b-fd3b-f4494da42c70@FreeBSD.org> <5B3EB443.50004@grosbein.net>
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On 7/5/18 5:13 PM, Eugene Grosbein wrote: > 06.07.2018 6:59, John Baldwin wrote: > >>> I'm not sure I understand the topic quite right, but please do not drop >>> MODULES_WITH_WORLD support at it allows us to quickly rebuild the kernel >>> in case of slight changes of its config file not changing ABI and/or >>> similar source changes without HUGE modules compilation overhead. >> >> This would not drop it, but it would mean that you can't necessarily kldload >> /boot/kernel.GENERIC/foo.ko while running some other kernel. > > And what's profit of such restriction? There were several cases > when I was forced to extract somemodule.ko from FreeBSD distribution files > and upload it to some customized installation such as FreeNAS or NAS4Free > or another one running custom kernel and having stripped-down module set out-of-the-box. > For example, ichwd.ko or something like that. And I was just happy I could do that and > that just work. Why should we break it? You would still do that by 'cd /sys/modules/foo; make; scp foo.ko somebox:' The profit of the restriction is performance. Making kernel modules generic makes them slower by forcing them to indirect certain lightweight operations through function calls that the kernel itself performs inline (and "tied" modules would inline these same things). The other benefit is that providing a convenient way to recompile modules from ports would alleviate KBI breakage for ports such as nvidia-graphics and virtualbox-ose-kmod that can break since they use parts of the kernel for which we do not guarantee KBI stability. -- John Baldwin
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