Date: Mon, 24 May 1999 02:21:57 +0800 (PHT) From: Orlando Andico <orly@mozcom.com> To: freebsd-questions@freebsd.org Subject: UFS, VM, scheduler, emulation questions Message-ID: <Pine.BSF.3.96.990524015817.2322A-100000@ice.mozcom.com>
next in thread | raw e-mail | index | archive | help
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?
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?
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)
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)?
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?
7) if I want to recompile my kernel and system using PGCC (is this
recommended?) which Makefiles do I alter?
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?
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)?
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)
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).
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()?
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?
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.
-------------------------------------------------------------------
Orlando Andico <orly@mozcom.com> +63 (2) 937-2293
Mosaic Communications, Inc. +63 (912) 800-8262
Promote bacteria.. it's the only culture some people have.
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-questions" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?Pine.BSF.3.96.990524015817.2322A-100000>