On Fri, 10 May 2013 09:20:46 -0400 Luiz Capitulino <lcapitulino@xxxxxxxxxx> wrote: > On Thu, 9 May 2013 18:15:19 -0300 > Rafael Aquini <aquini@xxxxxxxxxx> wrote: > > > On Thu, May 09, 2013 at 10:53:49AM -0400, Luiz Capitulino wrote: > > > Automatic ballooning consists of dynamically adjusting the guest's > > > balloon according to memory pressure in the host and in the guest. > > > > > > This commit implements the guest side of automatic balloning, which > > > basically consists of registering a shrinker callback with the kernel, > > > which will try to deflate the guest's balloon by the amount of pages > > > being requested. The shrinker callback is only registered if the host > > > supports the VIRTIO_BALLOON_F_AUTO_BALLOON feature bit. > > > > > > Automatic inflate is performed by the host. > > > > > > Here are some numbers. The test-case is to run 35 VMs (1G of RAM each) > > > in parallel doing a kernel build. Host has 32GB of RAM and 16GB of swap. > > > SWAP IN and SWAP OUT correspond to the number of pages swapped in and > > > swapped out, respectively. > > > > > > Auto-ballooning disabled: > > > > > > RUN TIME(s) SWAP IN SWAP OUT > > > > > > 1 634 930980 1588522 > > > 2 610 627422 1362174 > > > 3 649 1079847 1616367 > > > 4 543 953289 1635379 > > > 5 642 913237 1514000 > > > > > > Auto-ballooning enabled: > > > > > > RUN TIME(s) SWAP IN SWAP OUT > > > > > > 1 629 901 12537 > > > 2 624 981 18506 > > > 3 626 573 9085 > > > 4 631 2250 42534 > > > 5 627 1610 20808 > > > > > > Signed-off-by: Luiz Capitulino <lcapitulino@xxxxxxxxxx> > > > --- > > > > Nice work Luiz! Just allow me a silly question, though. > > I have 100% more chances of committing sillynesses than you, so please > go ahead. > > > Since your shrinker > > doesn't change the balloon target size, > > Which target size are you referring to? The one in the host (member num_pages > of VirtIOBalloon in QEMU)? > > If it the one in the host, then my understanding is that that member is only > used to communicate the new balloon target to the guest. The guest driver > will only read it when told (by the host) to do so, and when it does the > target value will be correct. > > Am I right? > > > as soon as the shrink round finishes the > > balloon will re-inflate again, won't it? Doesn't this cause a sort of "balloon > > thrashing" scenario, if both guest and host are suffering from memory pressure? Forgot to say that I didn't observe this in my testing. But I'll try harder as soon as we clarify which target size we're talking about. -- 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
