On Fri, Jul 30, 2004 at 06:06:54PM -0400, Gene Heskett wrote: > >>>The problem has gone away. I suspect that 4G/4G is broken. > > I'm certainly leaning in that direction also. Since turning on the 4G > switch, I've had literally dozens of Oppsen I hope you've been bugzilla'ing them. In many cases, these are caused by drivers doing things like dereferencing memory directly instead of using the correct means to copy to/from kernel/user space. Without a 4g/4g kernel, this happens to work, however in some cases, they can point to a security hole. This code was always broken, 4g/4g just makes it more obvious. A lot of issues have already been caught with this that had gone unnoticed for a long time, however its not unlikely that some remain, but without bug reports, we'll never know and they won't get fixed. > >> It sounds more "broken as designed", to be honest. It sounds as > >> though your setup is doing a *lot* of context switches between > >> user mode and kernel mode. The basic trade-off that 4G/4G flushes > >> the TLB each context switch, so that kernel and user both get > >> nearly 4 GB, and TLB flushes are expensive. > > Ouch! Does this help explain why my old mobo runnng a 1400XP athlon > could do 4.5 seti nits a day, and a 2800XP with this turned on is > only doing 6? The seti stuff should be CPU bound, and not making lots of transitions in/out of kernel space (which is the only time you really notice measurable overhead with 4g/4g). If it is doing lots of syscalls, something is wrong somewhere. Might be worth strace'ing the app and finding out what its doing. Dave
