OK, lets see what we've got; if I'm reading this vmstat correctly it's split
pretty
much between system time and wait (for IO):
procs -----------memory---------- ---swap-- -----io----
-system-- ----cpu----
r b swpd free buff cache si so bi bo
in cs us sy id wa
5 1 43964 120664 346700 2267880 0 0 17 18 16 13
2 0 97 0
0 0 43964 192872 343108 2216144 0 0 178 79081 13851 18234 2 30 45
23
1 1 43968 321924 339260 2051828 0 2 937 78577 14664 21679 3 34 33
30
1 4 43968 144504 329904 2311564 0 0 124 104639 21611 34747 3 46 8
44
1 2 43968 145264 319808 2323488 0 0 328 108663 24725 40773 3 39 19
40
1 4 43968 146860 317844 2325192 0 0 140 183331 38848 64357 2 46 4
47
now the way I'm reading that it's shifting about 100-180MB/s - (the bo column);
and reading your logs I think that's
to a spinny disc, so that's a perfectly respectable transfer rate; I wouldn't
have actually expected more than 100MB/s
though (i.e. 1000Mbps) assuming gigabit ether; what type of transfer were you
doing at the time - large file or lots of small
ones?
The 'wait' time doesn't worry me, given that it seems reasonable if it's
waiting for the disk.
To be honest I'd expect shifting 100MB/s over NFS would be pushing one
of your cores pretty hard, so I'm not too surprised your machine is
sluggish with that kind of load.
There are two things which might get some more detail:
1) Try and capture what happens during a 'hangup; is it a complete hang of
the server? Are there any log messages; if you perhaps watch a vmstat 1
during the period of the hangup what's going on (does the IO ever drop to being
much lower?)
2) Try to use something to see what's eating your system time (I'd bet on
the rtl ether card perhaps?); the perf command is good for seeing where
system time is going:
a) Start your load going
b) run sudo perf record -a
it generates a log file
c) After 30 seconds or so ctrl-c it
d) run sudo perf report --stdio > myperfreport
e) attach the myperfreport to this bugreport so we can see what your
kernel is doing.
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https://bugs.launchpad.net/bugs/1071978
Title:
nfs kernel server is very slow and causing high cpu load
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