Date: Sat, 28 Mar 2009 02:24:51 +0530 From: Prashant Vaibhav <prashant.vaibhav@gmail.com> To: Chuck Swiger <cswiger@mac.com> Cc: freebsd-current@freebsd.org Subject: Re: Improving the kernel/i386 timecounter performance (GSoC proposal) Message-ID: <17560ccf0903271354w167e42f8sc9f76e3f92486814@mail.gmail.com> In-Reply-To: <2C3C7185-CB37-4067-B2A9-A03B5B288606@mac.com> References: <11609492.9579.1238167614335.JavaMail.root@vms070.mailsrvcs.net> <49CD0405.1060704@samsco.org> <alpine.BSF.2.00.0903271821060.60642@fledge.watson.org> <49CD1B3D.3030103@samsco.org> <2C3C7185-CB37-4067-B2A9-A03B5B288606@mac.com>
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For those interested, XNU sources are available on watson also: http://fxr.watson.org/fxr/source/?v=xnu-1228 which doesn't need ADC login and has good cross-referencing of symbols. Latest is from darwin 9.0 corresponding to osx 10.5.0; there were a lot of changes to the vm part in 10.5.6 update. On Sat, Mar 28, 2009 at 12:46 AM, Chuck Swiger <cswiger@mac.com> wrote: > Hi, Scott & all-- > > > On Mar 27, 2009, at 11:30 AM, Scott Long wrote: > >> Robert Watson wrote: >> >>> On Fri, 27 Mar 2009, Scott Long wrote: >>> >>>> I've been talking about this for years. All I need is help with the VM >>>> magic to create the page on fork. I also want two pages, one global for >>>> gettimeofday (and any other global data we can think of) and one per-process >>>> for static data like getpid/getgid. >>>> >>> FWIW, there are some variations in schemes across OS's -- one extreme is >>> the Linux approach, which actually exports a mini shared library in ELF >>> format on the shared page, providing implementations of various services >>> (such as entering system calls), time stuff, etc. Less extreme are the >>> shared pages offered on Mac OS X, etc. >>> >> >> Yes, but I'd like to start somewhere, and considering that it's been >> impossible in _5_ years to get the 30 minutes of Peter or JeffR or JHB >> time to get the basic VM magic done, I'm keeping my expectations as >> modest as possible. >> > > I'm not entirely sure how close the Mach/xnu and FreeBSD implementations of > pmap_* stuff are, but the xnu code for commpage stuff is here: > > > http://www.opensource.apple.com/darwinsource/Current/xnu-1228.9.59/osfmk/i386/pmap.c [pmap_commpage32_init(), > pmap_commpage64_init()] > > http://www.opensource.apple.com/darwinsource/Current/xnu-1228.9.59/osfmk/i386/commpage/ [all > :-)] > > http://www.opensource.apple.com/darwinsource/Current/xnu-1228.9.59/osfmk/i386/commpage/commpage_gettimeofday.s [but > this one in particular] > > http://www.opensource.apple.com/darwinsource/Current/xnu-1228.9.59/osfmk/vm/vm_shared_region.c [cf > "COMM PAGE" comments, vm_commpage_init()] > > http://www.opensource.apple.com/darwinsource/Current/xnu-1228.9.59/bsd/kern/kern_fork.c [fork_create_child(), > procdup(), uses of pmap_map_sharedpage()] > > [ ADC login might be needed, otherwise I think rwatson has been importing > xnu periodically for TrustedBSD or other work, and might be able to provide > similar pointers... ] > > Regards, > -- > -Chuck > >
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