Re: nested KVM slower than QEMU with gnumach guest kernel

2014-12-15 Thread Paolo Bonzini
On 15/12/2014 01:09, Samuel Thibault wrote: Hello, Just FTR, it seems that the overhead is due to gnumach somtimes using the PIC quite a lot. It used not to be too much a concern with just kvm, but kvm on kvm becomes too expensive for that. I've fixed gnumach into being a lot more

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-12-14 Thread Samuel Thibault
Hello, Just FTR, it seems that the overhead is due to gnumach somtimes using the PIC quite a lot. It used not to be too much a concern with just kvm, but kvm on kvm becomes too expensive for that. I've fixed gnumach into being a lot more reasonable, and the performance issues got away. Samuel

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-23 Thread Samuel Thibault
Jan Kiszka, le Mon 17 Nov 2014 10:04:37 +0100, a écrit : On 2014-11-17 10:03, Samuel Thibault wrote: Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit : Do you know how gnumach timekeeping works? Does it have a timer that fires each 1ms? Which clock device is it using? It

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-23 Thread Samuel Thibault
Jan Kiszka, le Mon 17 Nov 2014 07:28:23 +0100, a écrit : I suppose this is a SMP host and guest? Does reducing CPUs to 1 change to picture? Oddly enough, putting my host into UniProcessor mode is making L1 realmode simulation awfully slow. That also happens when binding kvm on a single

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Samuel Thibault
Jan Kiszka, le Mon 17 Nov 2014 07:28:23 +0100, a écrit : AIUI, the external interrupt is 0xf6, i.e. Linux' IRQ_WORK_VECTOR. I however don't see any of them, neither in L0's /proc/interrupts, nor in L1's /proc/interrupts... I suppose this is a SMP host and guest? L0 is a hyperthreaded

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Gleb Natapov
On Sun, Nov 16, 2014 at 11:18:28PM +0100, Samuel Thibault wrote: Hello, Jan Kiszka, le Wed 12 Nov 2014 00:42:52 +0100, a écrit : On 2014-11-11 19:55, Samuel Thibault wrote: jenkins.debian.net is running inside a KVM VM, and it runs nested KVM guests for its installation attempts. This

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Samuel Thibault
Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit : Do you know how gnumach timekeeping works? Does it have a timer that fires each 1ms? Which clock device is it using? It uses the PIT every 10ms, in square mode (PIT_C0|PIT_SQUAREMODE|PIT_READMODE = 0x36). Samuel -- To unsubscribe

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Jan Kiszka
On 2014-11-17 10:03, Samuel Thibault wrote: Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit : Do you know how gnumach timekeeping works? Does it have a timer that fires each 1ms? Which clock device is it using? It uses the PIT every 10ms, in square mode

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Samuel Thibault
Jan Kiszka, le Mon 17 Nov 2014 10:04:37 +0100, a écrit : On 2014-11-17 10:03, Samuel Thibault wrote: Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit : Do you know how gnumach timekeeping works? Does it have a timer that fires each 1ms? Which clock device is it using? It

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Gleb Natapov
On Mon, Nov 17, 2014 at 10:10:25AM +0100, Samuel Thibault wrote: Jan Kiszka, le Mon 17 Nov 2014 10:04:37 +0100, a écrit : On 2014-11-17 10:03, Samuel Thibault wrote: Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit : Do you know how gnumach timekeeping works? Does it have a timer

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Samuel Thibault
Gleb Natapov, le Mon 17 Nov 2014 11:21:22 +0200, a écrit : On Mon, Nov 17, 2014 at 10:10:25AM +0100, Samuel Thibault wrote: Jan Kiszka, le Mon 17 Nov 2014 10:04:37 +0100, a écrit : On 2014-11-17 10:03, Samuel Thibault wrote: Gleb Natapov, le Mon 17 Nov 2014 10:58:45 +0200, a écrit :

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-17 Thread Samuel Thibault
Also, I have made gnumach show a timer counter, it does get PIT interrupts every 10ms as expected, not more often. Samuel -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-16 Thread Samuel Thibault
Hello, Jan Kiszka, le Wed 12 Nov 2014 00:42:52 +0100, a écrit : On 2014-11-11 19:55, Samuel Thibault wrote: jenkins.debian.net is running inside a KVM VM, and it runs nested KVM guests for its installation attempts. This goes fine with Linux kernels, but it is extremely slow with gnumach

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-16 Thread Jan Kiszka
On 2014-11-16 23:18, Samuel Thibault wrote: Hello, Jan Kiszka, le Wed 12 Nov 2014 00:42:52 +0100, a écrit : On 2014-11-11 19:55, Samuel Thibault wrote: jenkins.debian.net is running inside a KVM VM, and it runs nested KVM guests for its installation attempts. This goes fine with Linux

Re: nested KVM slower than QEMU with gnumach guest kernel

2014-11-11 Thread Jan Kiszka
On 2014-11-11 19:55, Samuel Thibault wrote: Hello, jenkins.debian.net is running inside a KVM VM, and it runs nested KVM guests for its installation attempts. This goes fine with Linux kernels, but it is extremely slow with gnumach kernels. I have reproduced the issue with my laptop with