Some tasks very slow after upgrade from Jessie to Stretch
Greetings.
Recently I cloned & upgraded a (virtual) build system, from Jessie to
Stretch,
and some tasks have become so slow that it hurts.
Look at 'git archive' for example, the tar part:
bob@build-stretch:/stuff/git/linux-stable$
time git archive v3.18.95 | perf stat tar xC /usr/src/test
Performance counter stats for 'tar xC /usr/src/test':
125849.626176 task-clock (msec) # 0.945 CPUs utilized
984 context-switches # 0.008 K/sec
3 cpu-migrations # 0.000 K/sec
135 page-faults # 0.001 K/sec
474,044,657,252 cycles # 3.767 GHz
190,146,876,098 stalled-cycles-frontend # 40.11% frontend cycles idle
122,803,944,538 stalled-cycles-backend # 25.91% backend cycles idle
511,500,080,424 instructions # 1.08 insn per cycle
# 0.37 stalled cycles
per insn
93,671,911,207 branches # 744.316 M/sec
2,810,364,901 branch-misses # 3.00% of all branches
133.182776679 seconds time elapsed
real 2m13.234s
user 0m4.268s
sys 2m6.748s
bob@build-jessie:/stuff/git/linux-stable$
time git archive v3.18.95 | perf stat tar xC /usr/src/test
Performance counter stats for 'tar xC /usr/src/test':
3908.736041 task-clock (msec) # 0.183 CPUs utilized
44,396 context-switches # 0.011 M/sec
134 cpu-migrations # 0.034 K/sec
133 page-faults # 0.034 K/sec
9,065,881,286 cycles # 2.319 GHz
7,497,944,714 stalled-cycles-frontend # 82.71% frontend cycles idle
6,277,695,339 stalled-cycles-backend # 69.25% backend cycles idle
2,987,957,839 instructions # 0.33 insns per cycle
# 2.51 stalled cycles
per insn
576,836,524 branches # 147.576 M/sec
14,885,342 branch-misses # 2.58% of all branches
21.365168109 seconds time elapsed
real 0m21.426s
user 0m4.664s
sys 0m6.164s
A bit slower now, on Stretch.
(and why are the perf numbers vastly different I wonder?)
Same thing for 'rm -rf'ing a kernel build tree, on the Stretch VM
it's multiple times slower - takes approx. two minutes.
KVM, same host, storage is virtio block device in LVM.
Setup has been working flawless for years.
Host is also Debian. Still Wheezy, but for a reason.
I've already
- tried different kernels on host and guest
- switched to ext3 from ext4 on guest (a bit faster, but not much)
- used a local git repo in guest (vs. network share which is default)
- asked the Googol
but no remedies yet.
What am I missing?
Has anyone experienced similar things after
upgrading from Jessie to Stretch?
Regards
Ingmar
--
assembled from 100% recycled electrons
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