We are taking about a full context switch here, not just entering/exiting the kernel. In my experience, x86 has traditionally been among the leaders here, because it has so few (architected) registers.
If you have numbers to the contrary, please post them. Don't just make unsubstantiated claims.
It's not nearly as expensive as you might think. For example, on a 733MHz Itanium, lmbench reports a 2 process context switch time of almost exactly 1 microsecond. For comparison, a 1.2GHz Athlon does this in about 0.88 microseconds. So yes, it's a little bit slower, but it's clearly right up there. Of course, by the time you get to 16 processes touching 64KB of data each, the Itanium does a context switch in about 60 microseconds and the Athlon is up in the 112 microsecond range.
If you didn't have a chance to catch our Linux/ia64 talk at Linux Expo last week, here is a nice summary (including pictures of all the slides and the boot screen):
Slashdot Mirror
The Millenium project is old. It was a hot topic when I was on the interviewing circuit---back in 1997!
Just check Rich Drave's homepage.
We are taking about a full context switch here, not just entering/exiting the kernel. In my experience, x86 has traditionally been among the leaders here, because it has so few (architected) registers.
If you have numbers to the contrary, please post them. Don't just make unsubstantiated claims.
It's not nearly as expensive as you might think. For example, on a 733MHz Itanium, lmbench reports a 2 process context switch time of almost exactly 1 microsecond. For comparison, a 1.2GHz Athlon does this in about 0.88 microseconds. So yes, it's a little bit slower, but it's clearly right up there. Of course, by the time you get to 16 processes touching 64KB of data each, the Itanium does a context switch in about 60 microseconds and the Athlon is up in the 112 microsecond range.
If you didn't have a chance to catch our Linux/ia64 talk at Linux Expo last week, here
C onferences/Merced.html
is a nice summary (including pictures of all the
slides and the boot screen):
http://marc.merlins.org/linux/linuxexpo99/Day3/