On Wed, 14 Feb 2007, Benjamin LaHaise wrote: > On Wed, Feb 14, 2007 at 11:45:23AM -0800, Davide Libenzi wrote: > > Sort of, except that the whole thing can complete syncronously w/out > > context switches. The real point of the whole fibrils/syslets solution is > > that kind of optimization. The solution is as good as it is now, for > > Except that You Can't Do That (tm). Try to predict beforehand if the code > path being followed will touch the FPU or SSE state, and you can't. There is > no way to avoid the context switch overhead, as you have to preserve things > so that whatever state is being returned to the user is as it was. Unless > you plan on resetting the state beforehand, but then you have to call into > arch specific code that ends up with a comparable overhead to the context > switch.
I think you may have mis-interpreted my words. *When* a schedule would block a synco execution try, then you do have a context switch. Noone argue that, and the code is clear. The sys_async_exec thread will block, and a newly woke up thread will re-emerge to sys_async_exec with a NULL returned to userspace. But in a "cachehit" case (no schedule happens during the syscall/*let execution), there is no context switch at all. That is the whole point of the optimization. - Davide - 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/
