> -----Original Message----- > From: Christoph Lameter [mailto:[EMAIL PROTECTED] > Sent: Friday, February 15, 2008 2:50 PM > To: Caitlin Bestler > Cc: linux-kernel@vger.kernel.org; [EMAIL PROTECTED]; [EMAIL PROTECTED]; > [EMAIL PROTECTED]; [EMAIL PROTECTED] > Subject: RE: [ofa-general] Re: Demand paging for memory regions > > On Fri, 15 Feb 2008, Caitlin Bestler wrote: > > > There isn't much point in the RDMA layer subscribing to mmu > > notifications > > if the specific RDMA device will not be able to react appropriately > when > > the notification occurs. I don't see how you get around needing to > know > > which devices are capable of supporting page migration (via > > suspend/resume > > or other mechanisms) and which can only respond to a page migration > by > > aborting connections. > > You either register callbacks if the device can react properly or you > dont. If you dont then the device will continue to have the problem > with > page pinning etc until someone comes around and implements the > mmu callbacks to fix these issues. > > I have doubts regarding the claim that some devices just cannot be made > to > suspend and resume appropriately. They obviously can be shutdown and so > its a matter of sequencing the things the right way. I.e. stop the app > wait for a quiet period then release resources etc. > >
That is true. What some devices will be unable to do is suspend and resume in a manner that is transparent to the application. However, for the duration required to re-arrange pages it is definitely feasible to do so transparently to the application. Presumably the Virtual Memory Manager would be more willing to take an action that is transparent to the user than one that is disruptive, although obviously as the owner of the physical memory it has the right to do either. -- 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/