Boot on various Amazon M6g (Graviton2 based) instances.
On a 64-core instance I observed a 10s reduction in buildworld times with
a previous version of this patch (only one build with and without the change).
I timed 10 make buildkernel -j64 runs with an empty obj. I ignored the first
tun as it was used to warm the cache. The user and real times showed no
significant change. The sys time shows the following improvement from an
earlier version of this patch. isync.sys is a full icache sync, no_isync
is with just a dsb & isb.
x isync.sys
+ no_isync.sys
+------------------------------------------------------------------------------+
| + x |
|+ + + + + x x x * ++x x x x|
| |___________M_______A___________|_______|_____A____________| |
+------------------------------------------------------------------------------+
N Min Max Median Avg Stddev
x 9 151.36 167.08 155.41 157.94778 5.6033289
+ 9 135.34 158.05 144.11 147.28333 8.2816167
Difference at 95.0% confidence
-10.6644 +/- 7.06605
-6.75188% +/- 4.38105%
(Student's t, pooled s = 7.07045)
I'm in the process of testing the current version of the patch.