Date: Mon, 01 Dec 2014 10:49:16 -0500 From: John Baldwin <jhb@freebsd.org> To: Alfred Perlstein <bright@mu.org> Cc: "svn-src-head@freebsd.org" <svn-src-head@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, Alfred Perlstein <alfred@freebsd.org>, "src-committers@freebsd.org" <src-committers@freebsd.org> Subject: Re: svn commit: r275136 - in head/sys: dev/e1000 dev/ixgbe kern sys Message-ID: <1762770.yx1cv63jp7@ralph.baldwin.cx> In-Reply-To: <872C180A-6ADD-469F-A801-3728DF134EEC@mu.org> References: <201411262019.sAQKJaw4043557@svn.freebsd.org> <39377603.10OyiSzjWY@ralph.baldwin.cx> <872C180A-6ADD-469F-A801-3728DF134EEC@mu.org>
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On Monday, December 01, 2014 07:19:13 AM Alfred Perlstein wrote: > John, > > Will work on a new revision based on feedback. > > Two things to note however: > > Already explored the idea of using kernel_sysctlbyname but rejected due to > following: > > It makes little sense to have a rw sysctl that only takes effect "some > times". This violates POLA at the expense of making code appear cleaner. > Expectation is that writable sysctls take effect or are read only. They are > not to be "write sometimes" unless we are to introduce a new flag. Instead > of going to a confusing model we consider some form of rw sysctl that can > set itself ro somehow. Otherwise people will be confused as to why nic > queues says N while actually M. What the rw->ro api would look like I have > no idea. Suggestions? This is only somewhat true. In the near distant future we will have a devctl tool which would let you do 'devctl detach igb0 && devctl attach igb0' which would honor your post-boot setting of hw.igb.num_queues. Instead what is important to understand about this particular sysctl node is that it only takes affect when a device is attached. However, there are other control knobs that also only affect future operations and not existing instances of objects, so I don't think this is that big of a leap. -- John Baldwin
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