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KVM: s390: reduce number of IO pins to 1 

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
This commit is contained in:
Christian Borntraeger 2020-06-17 10:36:20 +02:00
parent b3a9e3b962
commit 774911290c
1 changed files with 4 additions and 4 deletions
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8
arch/s390/include/asm/kvm_host.h
View File

@ -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 */