From: Christian Borntraeger <borntraeger@xxxxxxxxxx> The current number of KVM_IRQCHIP_NUM_PINS results in an order 3 allocation (32kb) for each guest start/restart. This can result in OOM killer activity even with free swap when the memory is fragmented enough: kernel: qemu-system-s39 invoked oom-killer: gfp_mask=0x440dc0(GFP_KERNEL_ACCOUNT|__GFP_COMP|__GFP_ZERO), order=3, oom_score_adj=0 kernel: CPU: 1 PID: 357274 Comm: qemu-system-s39 Kdump: loaded Not tainted 5.4.0-29-generic #33-Ubuntu kernel: Hardware name: IBM 8562 T02 Z06 (LPAR) kernel: Call Trace: kernel: ([<00000001f848fe2a>] show_stack+0x7a/0xc0) kernel: [<00000001f8d3437a>] dump_stack+0x8a/0xc0 kernel: [<00000001f8687032>] dump_header+0x62/0x258 kernel: [<00000001f8686122>] oom_kill_process+0x172/0x180 kernel: [<00000001f8686abe>] out_of_memory+0xee/0x580 kernel: [<00000001f86e66b8>] __alloc_pages_slowpath+0xd18/0xe90 kernel: [<00000001f86e6ad4>] __alloc_pages_nodemask+0x2a4/0x320 kernel: [<00000001f86b1ab4>] kmalloc_order+0x34/0xb0 kernel: [<00000001f86b1b62>] kmalloc_order_trace+0x32/0xe0 kernel: [<00000001f84bb806>] kvm_set_irq_routing+0xa6/0x2e0 kernel: [<00000001f84c99a4>] kvm_arch_vm_ioctl+0x544/0x9e0 kernel: [<00000001f84b8936>] kvm_vm_ioctl+0x396/0x760 kernel: [<00000001f875df66>] do_vfs_ioctl+0x376/0x690 kernel: [<00000001f875e304>] ksys_ioctl+0x84/0xb0 kernel: [<00000001f875e39a>] __s390x_sys_ioctl+0x2a/0x40 kernel: [<00000001f8d55424>] system_call+0xd8/0x2c8 As far as I can tell s390x does not use the iopins as we bail our for anything other than KVM_IRQ_ROUTING_S390_ADAPTER and the chip/pin is only used for KVM_IRQ_ROUTING_IRQCHIP. So let us use a small number to reduce the memory footprint. Signed-off-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> Reviewed-by: Cornelia Huck <cohuck@xxxxxxxxxx> Reviewed-by: David Hildenbrand <david@xxxxxxxxxx> Link: https://lore.kernel.org/r/20200617083620.5409-1-borntraeger@xxxxxxxxxx --- arch/s390/include/asm/kvm_host.h | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h index cee3cb6455a2..6ea0820e7c7f 100644 --- a/arch/s390/include/asm/kvm_host.h +++ b/arch/s390/include/asm/kvm_host.h @@ -31,12 +31,12 @@ #define KVM_USER_MEM_SLOTS 32 /* - * These seem to be used for allocating ->chip in the routing table, - * which we don't use. 4096 is an out-of-thin-air value. If we need - * to look at ->chip later on, we'll need to revisit this. + * These seem to be used for allocating ->chip in the routing table, which we + * don't use. 1 is as small as we can get to reduce the needed memory. If we + * need to look at ->chip later on, we'll need to revisit this. */ #define KVM_NR_IRQCHIPS 1 -#define KVM_IRQCHIP_NUM_PINS 4096 +#define KVM_IRQCHIP_NUM_PINS 1 #define KVM_HALT_POLL_NS_DEFAULT 50000 /* s390-specific vcpu->requests bit members */ -- 2.25.4
