Date: Mon, 24 May 1999 09:00:28 -0600 From: Oscar Bonilla <obonilla@fisicc-ufm.edu> To: Orlando Andico <orly@mozcom.com> Cc: freebsd-questions@FreeBSD.ORG Subject: Re: UFS, VM, scheduler, emulation questions Message-ID: <19990524090027.B327@fisicc-ufm.edu> In-Reply-To: <Pine.BSF.3.96.990524015817.2322A-100000@ice.mozcom.com>; from Orlando Andico on Mon, May 24, 1999 at 02:21:57AM %2B0800 References: <Pine.BSF.3.96.990524015817.2322A-100000@ice.mozcom.com>
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well, since no one has answered this one i might as well givi it a shot. WARNING: I'm not too sure about the answers. On Mon, May 24, 1999 at 02:21:57AM +0800, Orlando Andico wrote: > > Hello all, > > I'm a new FreeBSD user, although I've used Solaris 1 and 2, IRIX 5, and > Linux for several years and can probably consider myself an experienced > UNIX user. I have several questions about FreeBSD implementations. > > 1) FreeBSD 3.x ``feels'' faster than Linux on identical hardware. Is this > a scheduler feature (similar to Windows NT's ``boost foreground > application performance'') or some superior kernel feature that I'm > unaware of? i don't think freebsd is just "boosting" the forward application performance in a multiuser environment there can be many forward applications depending on how many users the system has. this isn't so in windows nt. > > 2) FreeBSD has a much faster filesystem (according to my simple tests) > than Solaris 2.6 x86. Of course Linux still holds the record for > filesystem writes because UFS synchronous metadata writes really slow down > filesystem performance. What changes were done to the FreeBSD > implementation of UFS to make this possible? is a UFS+ style metadata > logging (journaling) feature included? > > 3) there is an ioctl in SunOS/Solaris to DISABLE synchronous metadata > writes (forgot what it is though..) is this supported on FreeBSD? I think there's a way to disable sync metadata writes... i would check sysctl(8). Personally I use SoftUpdates. > > 4) does FreeBSD support LFS (large file summit) considering that UFS files > can be >>2GB in size according to the FAQ? or is this just PR (e.g. Linux > Reiserfs has 44-bit files, but the libc, etc, don't handle >2GB files) > hmm, beats me. > 5) how are pthreads implemented in FreeBSD 3.x? are these repackaged > Provenzano's threads, ``real'' kernel threads a la Linux (Linux threads > are processes, but fork overhead and ctx switch is very low on Linux as > evidenced by lmbench that it doesn't matter too much), or some other form > of userspace threads (e.g. FSU threads)? > FreeBSD supports POSIX Kernel Threads (a la linux) and pthreads (user threads). > 6) does FreeBSD retain the 4.4BSD/Mach VM system? it certainly consumes > much less memory for buffer cache than Linux, at least the stock setup. > When I run top(1) there is a parameter called "Wired." Is this the same as > wired (nonpageable) memory in the SVR4 VM model? > Don't know. > 7) if I want to recompile my kernel and system using PGCC (is this > recommended?) which Makefiles do I alter? > No, it's not recomended. FreeBSD 4.0 has egcs as the default compiler and 3.X has gcc 2.7.2.1 as the default. From what I've heard in the mailing lists compiling the kernel with anything but the default compiler is just a bad idea. > 8) can I use DMA on IDE drives like Linux does? what sort of I/O does > FreeBSD do on the wdc device? is it the dumb PIO that Linux does by > default, or is MaxMultsec, etc increased to improve performance? > Yes, altough it is not enabled by default. You have to add the flags 0xa0ffa0ff in your kernel config file to each of the IDE controllers. > 9) how good is the SMP support in FreeBSD (vis a vis Linux [which is not > that good, even in 2.2] and commercial OS's)? > I don't think any of the opensource OS's have great SMP support. I would give them fairly good or even usable SMP support. > 10) when using memfs on /tmp, is space used for files subtracted from > swap, like in Solaris 2.x? (e.g. if I fill up /tmp with big files, the > system won't be able to swap anymore) I've never used this so don't know. > > 11) I'm still keeping Linux around to run Informix Dynamic Server (as well > as the ultra-glitzy Red Hat 6.0 GNOME desktop). Will such a complicated > program (IDS) run under emulation? (it uses /etc/shadow instead of > /etc/master.passwd, makes extensive use of glibc2 threads, and does many > select(4096, ..) in there). Actually I've just set up informix dynamic server in my laptop under linux emmulation, i'm accessing it through apache + php3 with the informix module and since php needs to be linked to the informix libs i had to compile the whole thing for linux and run everything in linux emmulation mode... > > 12) how is poll() and select() implemented in the kernel? in the wake of > the Mindcraft fiasco much attention has been given to shortcomings in the > Linux scheduler (particularly in >2 CPU SMP boxes) and the linear scan > necessitated by poll() and select(). How is this issue addressed in BSD? > since wcarchive.cdrom.com handles thousands and thousands of clients, this > issue must have come up sometime.. also, are ``wake one'' select() > semantics implemented? what about sendfile()? > Use the source luke :) > 13) (my pet favorite) I like the packaging of Red Hat Linux (it's my other > OS) but the inexplicable ``it feels faster'' performance of FreeBSD makes > me wonder if anyone has done a ``reverse demon Penguin'' -- Linux > userland, FreeBSD kernel. Is this even possible? > everything's possible if you have source... just how much effort are you willing to put to accomplish something is a completly different matter. > 14) SGI is releasing XFS under an open-source license. Since XFS is > implemented on top of the vnode/vfs system, conceivably all free UNIX > variants would benefit. Is it worth it to run BSD on XFS, or is UFS > sufficient? > > > I realize these are a lot of questions, but the FAQ does not cover many of > them. It's easier to find answers on Linux because you can browse the > kernel mailing lists. I was hoping maybe there was a central repository > for questions of this nature. > regards, -Oscar -- For PGP Public Key: finger obonilla@fisicc-ufm.edu To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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