> > On the other side, the overhead you need to add for every single syscall
> > that might block for the M:N threads and the associated complications
> > which make it far harder to conform to POSIX IMHO far outweight the costs
> > of going into the kernel for a context switch.
>
> That really wasn't my question, Arjan said that switching real threads
> wasn't a context switch in the hardware sense, and I was asking if I
> missed something.
a hardware context switch is basically a CR3 change with associated tlb
flush. That is the part that is the most expensive of a context switch.
Just going into the kernel and getting out with a different EIP/ESP is
really cheap, in the order of "a few hundred cycles"; not a heck of a
lot more expensive than a simple getpid or other simple system call.
> It may be cheap, but it would seem to be a context
> switch none-the-less.
it includes a privilege level switch, not so much a full context
switch...
--
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
