[parisc-linux] Question about cache flushing and fork

[LaMont Jones]

On Tue, Dec 16, 2003 at 05:51:38PM -0500, John David Anglin wrote:
> > On Tue, Dec 16, 2003 at 12:06:57AM -0500, John David Anglin wrote:
> Is it possible to do PDC calls from user space under hpux to determine
> cache parameters?

The architecture requires that pdc calls be done at ring 0, with PSW.D=0,
so no.  Having said that, many of the interesting return values are
available from the kernel, either through sysconf or (sigh) /dev/kmem.

> I revised GCC's trampoline code to assume a line length of 32 instead
> of 64 on hppa64.  It can now flush arbitrarily long regions of memory.
> The test now passes.  This seems to imply that the cache length of a
> C200 under hpux11.00 is 32 bytes.

Cache line size is fixed on every CPU that I've seen, so OS shouldn't
matter...  One can assume a 16-byte cache line and it will work everywhere,
of course, although at 1/2 or 1/4 speed in many cases.  AFAIK, all PA1.1
machines use at least a 32 byte cache-line.

lamont