[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Implement 3-level event channel routines in Linux.
On Wed, 2013-01-02 at 21:12 +0000, Konrad Rzeszutek Wilk wrote: > On Wed, Jan 02, 2013 at 06:46:58PM +0000, Wei Liu wrote: > > On Wed, 2013-01-02 at 18:26 +0000, Konrad Rzeszutek Wilk wrote: > > > On Mon, Dec 31, 2012 at 06:38:54PM +0000, Wei Liu wrote: > > > > This patch series implements 3-level event channel routines in Linux > > > > kernel. > > > > > > > > My thought is that 3-level event channel is only useful for Dom0 or > > > > driver > > > > domain, so it is not enabled by default. Enable it with evtchn_level=3 > > > > in > > > > kernel command line. > > > > > > Could it be enabled dynamically? Say when we are close to exhausting the > > > amount of channels? Or if the machine has some large amount of memory and > > > hence would probably allocate many many guests? > > > > > > > Do you mean enabling this mechanism on the fly when Dom0 / driver domain > > is running? Or do you mean enabling it based on some metrics when > > starting up a domain? > > Either one. > > > > If it is the first case, who is responsible for initiating the switching > > process? It looks like it is Xen's responsibility to do the switch > > because Dom0 sometimes cannot know the true capability of underlying > > hardware. If it is Xen, then we need to add callback to poke Dom0 / > > driver domain. > > Huh? It would be as simple as Dom0 just figuring out that it is > at the end of the available events (b/c its close to the MAX) and > then transitioning to the 3-level one (if it can). > We need to manipulate various data structures. IMHO this makes implementation tricky and racy. > > > > For both cases, what do you have in mind for the metric that used to > > trigger the switch? How much RAM / how many CPUs is the threshold? > > No idea. At what point are we running out of the events? In practice, if you have hundreds or thousands of guests running you're likely of running out of event channels. I presume host capable of doing this has lots of RAM and CPUs... Wei. _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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