Mikael Pettersson writes:
> Something is causing the 4.4-rc kernels to only use half the CPU
> capacity of my Sun Blade 2500 (dual USIIIi). The kernel does detect
> both CPUs, but it doesn't seem to want to schedule processes on
> both of them. During CPU-intensive jobs like GCC bootstraps, 'top'
> indicates the machine is 50% idle and aggregate CPU usage is 100%
> (should be 200%). This is completely deterministic.
>
> Going back to 4.3.0 resolves the problems.
A git bisect identified the commit below as the culprit.
I've confirmed that reverting it from 4.4-rc7 solves the problem.
commit 52708d690b8be132ba9d294464625dbbdb9fa5df
Author: Nitin Gupta <nitin.m.gupta@xxxxxxxxxx>
Date: Mon Nov 2 16:30:24 2015 -0500
sparc64: Fix numa distance values
Orabug: 21896119
Use machine descriptor (MD) to get node latency
values instead of just using default values.
Testing:
On an T5-8 system with:
- total nodes = 8
- self latencies = 0x26d18
- latency to other nodes = 0x3a598
=> latency ratio = ~1.5
output of numactl --hardware
- before fix:
node distances:
node 0 1 2 3 4 5 6 7
0: 10 20 20 20 20 20 20 20
1: 20 10 20 20 20 20 20 20
2: 20 20 10 20 20 20 20 20
3: 20 20 20 10 20 20 20 20
4: 20 20 20 20 10 20 20 20
5: 20 20 20 20 20 10 20 20
6: 20 20 20 20 20 20 10 20
7: 20 20 20 20 20 20 20 10
- after fix:
node distances:
node 0 1 2 3 4 5 6 7
0: 10 15 15 15 15 15 15 15
1: 15 10 15 15 15 15 15 15
2: 15 15 10 15 15 15 15 15
3: 15 15 15 10 15 15 15 15
4: 15 15 15 15 10 15 15 15
5: 15 15 15 15 15 10 15 15
6: 15 15 15 15 15 15 10 15
7: 15 15 15 15 15 15 15 10
Signed-off-by: Nitin Gupta <nitin.m.gupta@xxxxxxxxxx>
Reviewed-by: Chris Hyser <chris.hyser@xxxxxxxxxx>
Reviewed-by: Santosh Shilimkar <santosh.shilimkar@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
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