Re: 5.4.20 - high load - lots of incoming data - small data read.

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Hi Jeff.

No, because the client "bacula-fd" is reading from the local
filesystem - here CephFS and sending it over the network to the server
with the tape-libraries attached to it.  Thus "ideal" receive == send
- which is also the pattern I see when using larger files (multiple
MB).

Is the per-file overhead many KB?

Jesper

On Mon, Apr 6, 2020 at 1:45 PM Jeff Layton <jlayton@xxxxxxxxxx> wrote:
>
> On Mon, 2020-04-06 at 10:04 +0200, Jesper Krogh wrote:
> > This is a CephFS client - its only purpose is to run the "filedaemon" of bacula
> > and transport data to the tape-library from CephFS - below 2 threads is
> > essentially doing something equivalent to
> >
> > find /cephfs/ -type f | xargs cat | nc server
> >
> > 2 threads only, load exploding and the "net read vs net write" has
> > more than 100x difference.
> >
>
> Makes sense. You're basically just reading in all of the data on this
> cephfs, so the receive is going to be much larger than the send.
>
> > Can anyone explain this as "normal" behaviour?
> > Server is a  VM with 16 "vCPU" and 16GB memory running libvirt/qemu
> >
> > jk@wombat:~$ w
> >  07:50:33 up 11:25,  1 user,  load average: 206.43, 76.23, 50.58
> > USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
> > jk       pts/0    10.194.133.42    06:54    0.00s  0.05s  0.00s w
> > jk@wombat:~$ dstat -ar
> > --total-cpu-usage-- -dsk/total- -net/total- ---paging-- ---system-- --io/total-
> > usr sys idl wai stl| read  writ| recv  send|  in   out | int   csw | read  writ
> >   0   0  98   1   0|  14k   34k|   0     0 |   3B   27B| 481   294 |0.55  0.73
> >   1   1   0  98   0|   0     0 |  60M  220k|   0     0 |6402  6182 |   0     0
> >   0   1   0  98   0|   0     0 |  69M  255k|   0     0 |7305  4339 |   0     0
> >   1   2   0  98   0|   0     0 |  76M  282k|   0     0 |7914  4886 |   0     0
> >   1   1   0  99   0|   0     0 |  70M  260k|   0     0 |7293  4444 |   0     0
> >   1   1   0  98   0|   0     0 |  80M  278k|   0     0 |8018  4931 |   0     0
> >   0   1   0  98   0|   0     0 |  60M  221k|   0     0 |6435  5951 |   0     0
> >   0   1   0  99   0|   0     0 |  59M  211k|   0     0 |6163  3584 |   0     0
> >   0   1   0  98   0|   0     0 |  64M  323k|   0     0 |6653  3881 |   0     0
> >   1   0   0  99   0|   0     0 |  61M  243k|   0     0 |6822  4401 |   0     0
> >   0   1   0  99   0|   0     0 |  55M  205k|   0     0 |5975  3518 |   0     0
> >   1   1   0  98   0|   0     0 |  68M  242k|   0     0 |7094  6544 |   0     0
> >   0   1   0  99   0|   0     0 |  58M  230k|   0     0 |6639  4178 |   0     0
> >   1   2   0  98   0|   0     0 |  61M  243k|   0     0 |7117  4477 |   0     0
> >   0   1   0  99   0|   0     0 |  61M  228k|   0     0 |6500  4078 |   0     0
> >   0   1   0  99   0|   0     0 |  65M  234k|   0     0 |6595  3914 |   0     0
> >   0   1   0  98   0|   0     0 |  64M  219k|   0     0 |6507  5755 |   0     0
> >   1   1   0  99   0|   0     0 |  64M  233k|   0     0 |6869  4153 |   0     0
> >   1   2   0  98   0|   0     0 |  63M  232k|   0     0 |6632  3907 |
> > 0     0 ^C
>
> Load average is high, but it looks like it's all just waiting on I/O.
>
> > jk@wombat:~$ w
> >  07:50:56 up 11:25,  1 user,  load average: 221.35, 88.07, 55.02
> > USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
> > jk       pts/0    10.194.133.42    06:54    0.00s  0.05s  0.00s w
> > jk@wombat:~$
> >
> --
> Jeff Layton <jlayton@xxxxxxxxxx>
>



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