Date: Sat, 14 Oct 1995 15:44:30 -0700 From: Pete Delaney <pete@RockyMountain.rahul.net> To: terry@lambert.org Cc: jehamby@lightside.com, pete@RockyMountain.rahul.net, freebsd-hackers@FreeBSD.ORG, ports@FreeBSD.ORG, netbsd-ports@netbsd.org Subject: Re: Netscape 2.0beta1 - Port of HotJava to FreeBSD and NetBSD More Usefull? Message-ID: <199510142244.AA06130@RockyMountain.rahul.net>
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> > > > > I heard there was some fairly good progress being made on a Linux port. > > > > Is this true? Because if the Linux people have a working version, then a > > > > FreeBSD/NetBSD version would be almost trivial from there. > > > > > > Not so. According to Linus (and Alan Cox), Linux has kernel > > > multithreading. > > > > I suppose a thread library, like SusOS has, is likely necessary, but I > > really doubt kernel multithreading is necessary. Any bets? > > Sun's multithreading as of Solaris is a kernl/user space cooperative > model, with n kernel threads being mapped to m user space threads > (m >= n). Sure for Slowaris this approach makes sense, but Slowaris runs noticably lower on sun4c that SunOS does. The added flexabilty of SMP in the kernel forces a non-trivial performance impact on the kernel. Pyramid used macros that only kicked in if compiled for SMP, this avoids the problem if done carefully. Etherway, SMP is a lot of work. > > So the only real threading on Solaris is kernel. Sure, but since most hackers will likely be using old Sun4c's, which cost from $100 to $400 for the CPU board, I doubt the performance penality for SMP is worth it for most FreeBSD users. Besides, waiting to get SMP working delays porting HotJava, I suspect that it's better to use a thread library like SunOS uses. > > The SunOS LWP library (a purely aioread/aiowrite/aiowait/aiocancel based > task switcher) is supported via the kernel calls for binaray compatability > reasons, but an lwp library is not provided for Solaris: you are expected > to use the kernel thread model. What do you mean I'm expected to use a kernel thread model? I assume you mean in the HotJava code. I expect it's far easier to change any dependancies in HotJava for Kernel bases threads than it is to implement SMP. > > SVR4.2 and above uses the same model. I read the SVR4.2 docs on SMP, and I found the Sequent SMP cod, which is 4.2 based, much nicer. If we are going to make NetBSD SMP, I wonder if it's worthwhile to ask Sequent if they would donate their Dynix OS SMP changes, which has been replace with a SVR4 code base, to the NetBSD community for integration into NetBSD. In the mean time, I would think porting HotJava from a Linux port might be worthwhile. I heard from some of the guys at sequent that Sun got Slowaris faster with help from Cray. Hacking SMP in netbsd is likely a major effort. How far along is Jack Vogel on his SMP hacks? > > > Terry Lambert > terry@lambert.org > --- > Any opinions in this posting are my own and not those of my present > or previous employers.
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