[RFC PATCH 00/17] KVM: arm64: Parallelize stage 2 fault handling

[Oliver Upton]

On Fri, Apr 15, 2022 at 09:58:44PM +0000, Oliver Upton wrote:

[...]

> 
> Smoke tested with KVM selftests + kvm_page_table_test w/ 2M hugetlb to
> exercise the table pruning code. Haven't done anything beyond this,
> sending as an RFC now to get eyes on the code.

Ok, got around to testing this thing a bit harder. Keep in mind that
permission faults at PAGE_SIZE granularity already go on the read side
of the lock. I used the dirty_log_perf_test with 4G/vCPU and anonymous
THP all the way up to 48 vCPUs. Here is the data as it compares to
5.18-rc2.

Dirty log time (split 2M -> 4K):

+-------+----------+-------------------+
| vCPUs | 5.18-rc2 | 5.18-rc2 + series |
+-------+----------+-------------------+
|     1 | 0.83s    | 0.85s             |
|     2 | 0.95s    | 1.07s             |
|     4 | 2.65s    | 1.13s             |
|     8 | 4.88s    | 1.33s             |
|    16 | 9.71s    | 1.73s             |
|    32 | 20.43s   | 3.99s             |
|    48 | 29.15s   | 6.28s             |
+-------+----------+-------------------+

The scaling of prefaulting pass looks better too (same config):

+-------+----------+-------------------+
| vCPUs | 5.18-rc2 | 5.18-rc2 + series |
+-------+----------+-------------------+
|     1 | 0.42s    | 0.18s             |
|     2 | 0.55s    | 0.19s             |
|     4 | 0.79s    | 0.27s             |
|     8 | 1.29s    | 0.35s             |
|    16 | 2.03s    | 0.53s             |
|    32 | 4.03s    | 1.01s             |
|    48 | 6.10s    | 1.51s             |
+-------+----------+-------------------+

--
Thanks,
Oliver