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> While this message is a few days late, Linux does work on more than 2
> processors.
>
> I don't know the full details, but before the 2.2 series of kernels for
> Linux was released, someone on the Linux-SMP list showed their boot
> messages.
>
> It was on a Sun (don't know which one) Sparc system with either 12, 20, or
> 22 processors (I don't remember how many -- search the archives if anyone is
> really interested). While not a typical Linux installation and not Intel, it
> did work with more than 4 processors.
When you get above two processor, the SMP method used by Linux, FreeBSD,
BSD/OS, etc do not work as well as a kernel-level SMP like Solaris.
In the Linux/*BSD SMP, you can only run a kernel call on one processor
at a time. With only two cpu's, the odds a two running processes both
needing to do a kernel call at the same time are rare. As you get more
processors, the chance of kernel contension gets higher, and you get
more cpu's running idle becuase there are is no process that has
non-kernel-level demands for a cpu.
> I don't know how FreeBSD SMP compares to Linux. Linux SMP works quite nicely
> on the systems I have running (dual PPro 200 with 256 meg RAM and IDE hard
> drives). The IDE drives are definitely a bottleneck on large table queries.
> I'm looking to move to SCSI.
IDE does not allow multiple outstanding request, can not access multiple
disks at the same time, and requires more CPU to do the transfer than
SCSI. This last point is normally forgotten.
--
Bruce Momjian | http://www.op.net/~candle
maillist@candle.pha.pa.us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
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