From mboxrd@z Thu Jan 1 00:00:00 1970 From: Avi Kivity Subject: Re: [PATCH][RFC] kvm-scheduler integration Date: Mon, 09 Jul 2007 09:39:43 +0300 Message-ID: <4691D82F.3030401@qumranet.com> References: <11838994974161-git-send-email-avi@qumranet.com> <20070708133539.GA12597@elte.hu> <4690E973.7000606@qumranet.com> <20070708134850.GB22911@elte.hu> <1183937563.6005.365.camel@localhost.localdomain> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Cc: kvm-devel-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Rusty Russell Return-path: In-Reply-To: <1183937563.6005.365.camel-bi+AKbBUZKY6gyzm1THtWbp2dZbC/Bob@public.gmane.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org Errors-To: kvm-devel-bounces-5NWGOfrQmneRv+LV9MX5uipxlwaOVQ5f@public.gmane.org List-Id: kvm.vger.kernel.org Rusty Russell wrote: > On Sun, 2007-07-08 at 15:48 +0200, Ingo Molnar wrote: > >> * Avi Kivity wrote: >> >> >>>>> +#ifdef CONFIG_SCHED_KVM >>>>> +static __read_mostly struct sched_kvm_hooks kvm_hooks; >>>>> +#endif >>>>> >>>> please just add a current->put_vcpu() function pointer instead of >>>> this hooks thing. >>>> >>> Won't that increase task_struct (16 bytes on 64-bit) unnecessarily? >>> The function pointers are common to all virtual machines. >>> >> well, this function pointer could then be reused by other virtual >> machines as well, couldnt it? If the task struct overhead is a problem >> (it really isnt, and it's dependent on CONFIG_KVM) then we could switch >> it around to a notifier-alike mechanism. >> > > OK, this patch is *ugly*. Not that there's anything wrong with a patch > which says "I'm going to preempt you", but making it kvm-specific is > ugly. ISTR times past where I wanted such a hook, although none spring > immediately into my pre-coffee brain. > > I think a "struct preempt_ops *" and a "void *preempt_ops_data" inside > every task struct is a better idea. Call the config option > PREEMPT_SCHED_HOOKS and now there's nothing kvm-specific about it... > I considered that, but your proposal does not allow a single task to have multiple preemption hooks installed (hookers?!). Since in general there's no reason to suppose that users would be mutually exclusive, we need to have a struct hlist of these things. All in all this seemed to indicate that the second user should have the honor of figuring out that stuff. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. ------------------------------------------------------------------------- This SF.net email is sponsored by DB2 Express Download DB2 Express C - the FREE version of DB2 express and take control of your XML. No limits. Just data. Click to get it now. http://sourceforge.net/powerbar/db2/