linux/virt/kvm
Longpeng(Mike) 515a0c79e7 kvm: irqfd: avoid update unmodified entries of the routing
All of the irqfds would to be updated when update the irq
routing, it's too expensive if there're too many irqfds.

However we can reduce the cost by avoid some unnecessary
updates. For irqs of MSI type on X86, the update can be
saved if the msi values are not change.

The vfio migration could receives benefit from this optimi-
zaiton. The test VM has 128 vcpus and 8 VF (with 65 vectors
enabled), so the VM has more than 520 irqfds. We mesure the
cost of the vfio_msix_enable (in QEMU, it would set routing
for each irqfd) for each VF, and we can see the total cost
can be significantly reduced.

                Origin         Apply this Patch
1st             8              4
2nd             15             5
3rd             22             6
4th             24             6
5th             36             7
6th             44             7
7th             51             8
8th             58             8
Total           258ms          51ms

We're also tring to optimize the QEMU part [1], but it's still
worth to optimize the KVM to gain more benefits.

[1] https://lists.gnu.org/archive/html/qemu-devel/2021-08/msg04215.html

Signed-off-by: Longpeng(Mike) <longpeng2@huawei.com>
Message-Id: <20210827080003.2689-1-longpeng2@huawei.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2021-09-30 04:27:10 -04:00
..
async_pf.c mm/gup: remove task_struct pointer for all gup code 2020-08-12 10:58:04 -07:00
async_pf.h treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 504 2019-06-19 17:09:56 +02:00
binary_stats.c KVM: stats: remove dead stores 2021-08-13 03:35:15 -04:00
coalesced_mmio.c KVM: mmio: Fix use-after-free Read in kvm_vm_ioctl_unregister_coalesced_mmio 2021-07-14 12:17:56 -04:00
coalesced_mmio.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
dirty_ring.c KVM: Drop unused kvm_dirty_gfn_invalid() 2021-09-06 08:23:46 -04:00
eventfd.c kvm: irqfd: avoid update unmodified entries of the routing 2021-09-30 04:27:10 -04:00
irqchip.c KVM/arm updates for 5.3 2019-07-11 15:14:16 +02:00
Kconfig kvm: add PM-notifier 2021-06-17 13:09:32 -04:00
kvm_main.c kvm: rename KVM_MAX_VCPU_ID to KVM_MAX_VCPU_IDS 2021-09-30 04:27:05 -04:00
mmu_lock.h KVM: x86/mmu: Use an rwlock for the x86 MMU 2021-02-04 05:27:43 -05:00
vfio.c treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 500 2019-06-19 17:09:55 +02:00
vfio.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00