powerpc/topology: Override cpu_smt_mask
On Power9, a pair of SMT4 cores can be presented by the firmware as a SMT8
core for backward compatibility reasons, with the fusion of two SMT4 cores.
Powerpc allows LPARs to be live migrated from Power8 to Power9. Existing
software developed/configured for Power8, expects to see a SMT8 core.
In order to maintain userspace backward compatibility (with Power8 chips in
case of Power9) in enterprise Linux systems, the topology_sibling_cpumask
has to be set to SMT8 core.
cpu_smt_mask() should generally point to the cpu mask of the SMT4 core.
Hence override the default cpu_smt_mask() to be powerpc specific
allowing for better scheduling behaviour on Power.
schbench
(latency measured in usecs, so lesser is better)
Without patch With patch
Latency percentiles (usec) Latency percentiles (usec)
50.0000th: 34 50.0000th: 38
75.0000th: 47 75.0000th: 52
90.0000th: 54 90.0000th: 60
95.0000th: 57 95.0000th: 64
*99.0000th: 62 *99.0000th: 72
99.5000th: 65 99.5000th: 75
99.9000th: 76 99.9000th: 3452
min=0, max=9205 min=0, max=9344
schbench (With Cede disabled)
Without patch With patch
Latency percentiles (usec) Latency percentiles (usec)
50.0000th: 20 50.0000th: 21
75.0000th: 28 75.0000th: 29
90.0000th: 33 90.0000th: 34
95.0000th: 35 95.0000th: 37
*99.0000th: 40 *99.0000th: 40
99.5000th: 48 99.5000th: 42
99.9000th: 94 99.9000th: 79
min=0, max=791 min=0, max=791
perf bench sched pipe
usec/ops : lesser is better
Without patch
N Min Max Median Avg Stddev
101 5.095113 5.595269 5.204842 5.
2298776 0.
10762713
5.10 - 5.15 : ################################################## 23% (24)
5.15 - 5.20 : ############################################# 21% (22)
5.20 - 5.25 : ################################################## 23% (24)
5.25 - 5.30 : ######################### 11% (12)
5.30 - 5.35 : ########## 4% (5)
5.35 - 5.40 : ######## 3% (4)
5.40 - 5.45 : ######## 3% (4)
5.45 - 5.50 : #### 1% (2)
5.50 - 5.55 : ## 0% (1)
5.55 - 5.60 : #### 1% (2)
With patch
N Min Max Median Avg Stddev
101 5.134675 8.524719 5.207658 5.
2780985 0.
34911969
5.1 - 5.5 : ################################################## 94% (95)
5.5 - 5.8 : ## 3% (4)
5.8 - 6.2 : 0% (1)
6.2 - 6.5 :
6.5 - 6.8 :
6.8 - 7.2 :
7.2 - 7.5 :
7.5 - 7.8 :
7.8 - 8.2 :
8.2 - 8.5 :
perf bench sched pipe (cede disabled)
usec/ops : lesser is better
Without patch
N Min Max Median Avg Stddev
101 7.884227 12.576538 7.956474 8.
0170722 0.
46159054
7.9 - 8.4 : ################################################## 99% (100)
8.4 - 8.8 :
8.8 - 9.3 :
9.3 - 9.8 :
9.8 - 10.2 :
10.2 - 10.7 :
10.7 - 11.2 :
11.2 - 11.6 :
11.6 - 12.1 :
12.1 - 12.6 :
With patch
N Min Max Median Avg Stddev
101 7.956021 8.217284 8.015615 8.
0283866 0.
049844967
7.96 - 7.98 : ###################### 12% (13)
7.98 - 8.01 : ################################################## 28% (29)
8.01 - 8.03 : #################################### 20% (21)
8.03 - 8.06 : ######################### 14% (15)
8.06 - 8.09 : ###################### 12% (13)
8.09 - 8.11 : ###### 3% (4)
8.11 - 8.14 : ### 1% (2)
8.14 - 8.17 : ### 1% (2)
8.17 - 8.19 :
8.19 - 8.22 : # 0% (1)
Observations: With the patch, the initial run/iteration takes a slight
longer time. This can be attributed to the fact that now we pick a CPU
from a idle core which could be sleep mode. Once we remove the cede,
state the numbers improve in favour of the patch.
ebizzy:
transactions per second (higher is better)
without patch
N Min Max Median Avg Stddev
100
1018433 1304470 1193208 1182315.7 60018.733
1018433 -
1047037 : ###### 3% (3)
1047037 -
1075640 : ######## 4% (4)
1075640 -
1104244 : ######## 4% (4)
1104244 -
1132848 : ############### 7% (7)
1132848 -
1161452 : #################################### 17% (17)
1161452 -
1190055 : ########################## 12% (12)
1190055 -
1218659 : ############################################# 21% (21)
1218659 -
1247263 : ################################################## 23% (23)
1247263 -
1275866 : ######## 4% (4)
1275866 -
1304470 : ######## 4% (4)
with patch
N Min Max Median Avg Stddev
100 967014
1292938 1208819 1185281.8 69815.851
967014 - 999606 : ## 1% (1)
999606 -
1032199 : ## 1% (1)
1032199 -
1064791 : ############ 6% (6)
1064791 -
1097384 : ########## 5% (5)
1097384 -
1129976 : ################## 9% (9)
1129976 -
1162568 : #################### 10% (10)
1162568 -
1195161 : ########################## 13% (13)
1195161 -
1227753 : ############################################ 22% (22)
1227753 -
1260346 : ################################################## 25% (25)
1260346 -
1292938 : ############## 7% (7)
Observations: Not much changes, ebizzy is not much impacted.
Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200807074517.27957-2-srikar@linux.vnet.ibm.com
OSDN Git Service
