On Mon, 17 Nov 2008, Ingo Molnar wrote: > > syscall entry instruction costs - unavoidable security checks, etc. - > hardware costs. Yes. One thing to look out for on x86 is the system call _return_ path. It doesn't show up in kernel profiles (it shows up as user costs), and we had a bug where auditing essentially always caused us to use 'iret' instead of 'sysret' because it took us the long way around. And profiling doesn't show it, but things like lmbench did, iret being about five times slower than sysret. But yes: > -ENTRY(system_call_after_swapgs) > +.globl system_call_after_swapgs > +system_call_after_swapgs: This definitely makes sense. We definitely do not want to align that special case. Linus -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
