| From e8254b6b6c46cd6a869ae3d07c882ea557f60a3b Mon Sep 17 00:00:00 2001 |
| From: Sasha Levin <sashal@kernel.org> |
| Date: Wed, 17 Jun 2020 10:36:20 +0200 |
| Subject: KVM: s390: reduce number of IO pins to 1 |
| |
| From: Christian Borntraeger <borntraeger@de.ibm.com> |
| |
| [ Upstream commit 774911290c589e98e3638e73b24b0a4d4530e97c ] |
| |
| 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@de.ibm.com> |
| Reviewed-by: Cornelia Huck <cohuck@redhat.com> |
| Reviewed-by: David Hildenbrand <david@redhat.com> |
| Link: https://lore.kernel.org/r/20200617083620.5409-1-borntraeger@de.ibm.com |
| Signed-off-by: Sasha Levin <sashal@kernel.org> |
| --- |
| 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 abe60268335d2..0fe5600a037e4 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 */ |
| -- |
| 2.25.1 |
| |