On Wed, Jun 17, 2009 at 11:02:06AM -0400, Gregory Haskins wrote: > Michael S. Tsirkin wrote: > > On Tue, Jun 16, 2009 at 02:09:38PM -0400, Gregory Haskins wrote: > > > >>> What do you mean by copy_to_user(other->mm) here? If you are going to switch > >>> to another mm, then I think current->mm must be valid (I think it's not enough > >>> that you can sleep). So preemptible() might not be enough. > >>> > >>> > >> I dont currently use switch_mm, if that is what you mean. I save the > >> task_struct into the appropriate context so current->mm doesn't matter > >> to me. I never use it. All I need (afaik) is to acquire the proper > >> mutex first. I am not an MM expert, so perhaps I have this wrong but it > >> does appear to work properly even from kthread context. > >> > >> -Greg > >> > >> > >> > > > > I think I saw get_user_pages + memcpy in your patch. Yes, that works > > without switching contexts but it's slower than copy to user if you are > > in the right context, and AFAIK it's slower than get_user_pages_fast. > > > > > Yeah, understood. It will definitely be interesting to try that > optimization with switch_mm that you suggested. BTW, I'm kind of confused - in your patch you do get_task_struct: does this guarantee that mm is not going aways? > On that front, would "if (p == current)" still work even if we don't > have the "signal_task()" hint? > Donnu. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
