[Solved] System with Linux 3.14 (intel_pstate) noticeable less...

Question

... responsive and significantly slower (some numbers below) under light/medium workload, even when compared with ondemand (up_threshold 95). What happened to that famous race to idle concept? Relevant bug report https://bugzilla.kernel.org/show_bug.cgi?id=70941 (apparently "fixed")
"Tests" on 2500k (4 cores SB @ stock freq.):
1) in tmpfs
for num in {1..50000}; do
dd if=/dev/urandom of=file$num.log bs=10k count=1
done
2) Sunspider 1.0.2 https://www.webkit.org/perf/sunspider-1 … river.html
3) rsync in tmpfs
Results:
Linux 3.14 intel_pstate /w powersave governor (default)
1)
real 2m7.609s
user 0m5.060s
sys 0m12.797s
2)
run 1 - 200.9ms +/- 1.9%
run 2 - 199.1ms +/- 1.9%
run 3 - 202.3ms +/- 1.0%
3)
first run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m1.692s
user 0m2.033s
sys 0m0.887s
second run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m0.578s
user 0m0.267s
sys 0m0.270s
Linux 3.14 ondemand up threshold 95 (intel_pstate=disable)
1)
real 1m35.773s
user 0m4.947s
sys 0m12.890s
2)
run 1 - 154.3ms +/- 0.8%
run 2 - 155.2ms +/- 0.8%
run 3 - 154.0ms +/- 0.7%
3)
first run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m1.097s
user 0m1.210s
sys 0m0.620s
second run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m0.473s
user 0m0.200s
sys 0m0.230s
Linux 3.13.9 intel_pstate /w powersave governor (default)
1)
real 1m3.553s
user 0m15.353s
sys 0m42.444s
2)
run 1 - 155.4ms +/- 0.9%
run 2 - 154.6ms +/- 0.5%
run 3 - 153.9ms +/- 1.1%
3)
first run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m1.014s
user 0m1.351s
sys 0m0.353s
second run: $ time rsync -aAX /tmp/modules /tmp/test
real 0m0.344s
user 0m0.154s
sys 0m0.149s
Last edited by gedgon (2014-06-24 09:29:23)

Answer 1

same here (Fedora 20). i7-4800MQ on 3.13 in-rest at 2.7 GHz, on 3.14 800MHz. Boot times 30% up. A wrapper around commands shows elapsed times for "systemd-analyze blame". Both kernel boots in "powersave" governor:
4 times command execution on kernel 3.13:
.121303
.124094
.122310
.125066
and the same in kernel 3.14:
.442166
.442842
.447207
.430436
upping the --min through cpupower to 2.7 GHz I stell don't get the perf of 3.13:
.139518
.140489
.139541
.136105