2:32 a.m.
On Thu, Aug 01, 2019 at 03:44:31PM -0700, ivo welch wrote:
hi richard---arthur and I are working with nbdkit v1.12.3 on
qemu/kvm.
we found that our linux (ubuntu 16.04 32-bit) boot time from a local .img
file went from about 10 seconds to about 3 minutes when using the nbdkit
file plugin instead of directly connecting qemu to the file. on further
inspection with bonnie++, we think the problem may be related to poor
random seek performance:
In general I would expect some slowdown between using qemu directly
against a file and using qemu -> nbd driver -> nbdkit -> file, but not
nearly as much as you observed.
This is running bonnie++ inside the guest?
Are qemu & nbdkit running on the same machine? Are you using a TCP
port or a Unix domain socket? (If TCP you may want to consider
commits d088bf45, 0721aa9579 and 3842a080c). Which version of qemu is
it?
Rich.
DIRECT FROM QEMU TO .IMG FILE:
------------------------------------------------------------------------------------------------------------------------------
Version 1.97 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
TEST 4G 109468 11 58405 16 180613 33
3204 147
Latency 7125ms 5812ms 131ms
101ms
------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------
NBDKIT:
------------------------------------------------------------------------------------------------------------------------------
1.97,1.97,TEST,1,1564697809,4G,,,,109468,11,58405,16,,,180613,33,3204,147,,,,,,,,,,,,,,,,,,,7125ms,5812ms,,131ms,101ms,,,,,,
Version 1.97 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
TEST 4G 105761 11 58992 14 178472 30
39.3 6
Latency 8166ms 3683ms 187ms
1197ms
------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------
NBDKIT (-fv):
------------------------------------------------------------------------------------------------------------------------------
1.97,1.97,TEST,1,1564698256,4G,,,,105761,11,58992,14,,,178472,30,39.3,6,,,,,,,,,,,,,,,,,,,8166ms,3683ms,,187ms,1197ms,,,,,,
Version 1.97 ------Sequential Output------ --Sequential Input-
--Random-
Concurrency 1 -Per Chr- --Block-- -Rewrite- -Per Chr- --Block--
--Seeks--
Machine Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP /sec
%CP
TEST 4G 104941 10 56501 14 160557 28
39.9 6
Latency 15318ms 5200ms 101ms
1152ms
1.97,1.97,TEST,1,1564695086,4G,,,,104941,10,56501,14,,,160557,28,39.9,6,,,,,,,,,,,,,,,,,,,15318ms,5200ms,,101ms,1152ms,,,,,,
------------------------------------------------------------------------------------------------------------------------------
------------------------------------------------------------------------------------------------------------------------------
is this an error on our part? do you have any recommendations on what we
could investigate next?
regards,
/iaw
--
Ivo Welch (ivo.welch(a)ucla.edu)
http://www.ivo-welch.info/
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
libguestfs lets you edit virtual machines. Supports shell scripting,
bindings from many languages. http://libguestfs.org
2:44 a.m.
New subject: nbdkit random seek performance
BTW you might be interested in a ‘fio’ backend I wrote for testing NBD
servers. The current public version is here:
https://www.spinics.net/lists/fio/msg07831.html
but I also now have a version based on libnbd although it's not quite
ready for use.
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
7:23 p.m.
New subject: nbdkit random seek performance
Hi Rich---we were running qemu and nbdkit on the same machine, connecting
over tcp. after updating to the latest development version of nbdkit
(containing the commits you mentioned), everything works perfectly. running
bonnie++ inside the guest indicates that connecting qemu to nbdkit has
performance similar to or better than connecting qemu directly to the disk
image. thanks a lot for your work and advice--we just wanted to drop you
this note to tell you about our experience, in case someone else ends up
having similar questions.
regards,
/ivo and arthur
--
Ivo Welch (ivo.welch(a)ucla.edu)
http://www.ivo-welch.info/
J. Fred Weston Distinguished Professor of Finance, UCLA Anderson
On Fri, Aug 2, 2019 at 12:49 AM Richard W.M. Jones <rjones(a)redhat.com>
wrote:
BTW you might be interested in a ‘fio’ backend I wrote for testing NBD
servers. The current public version is here:
https://www.spinics.net/lists/fio/msg07831.html
but I also now have a version based on libnbd although it's not quite
ready for use.
Rich.
--
Richard Jones, Virtualization Group, Red Hat
http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines. Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v
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Richard W.M. Jones