Re: NFS3 + kerberos: performance issues

[Vladimir Elisseev <vovan@vovan.nl>]

All of the accounts, except very limited amount, are in LDAP, and as I
can see user information is identical on server and client. As for my
tests, below are all the details. Difference in speed while copying a
lot of small files is _huge_... I'd appreciate if somebody more familiar
with NFS/kerberos combination can provide a kind of explanation. 

Regards,
Vlad.

* Local directory is /mnt/data/tmp/coreboot/src
# find x86/ | wc -l
296
# du -csh x86
1.5M	x86
1.5M	total
* First try without kerberos: grep /mnt/tmp/ /proc/mounts
nfs:/mnt/tmp /mnt/tmp nfs
rw,noatime,vers=3,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=sys,mountaddr=192.168.1.219,mountvers=3,mountport=32767,mountproto=tcp,local_lock=none,addr=192.168.1.219 0 0
# time cp -i -arv /mnt/data/tmp/coreboot/src/arch/x86 /mnt/tmp/x86 
cp -i -arv /mnt/data/tmp/coreboot/src/arch/x86 /mnt/tmp/x86 0.01s user
0.04s system 10% cpu 0.476 total

* Second try with kerberos: grep /mnt/tmp/ /proc/mounts
nfs:/mnt/tmp /mnt/tmp nfs
rw,noatime,vers=3,rsize=524288,wsize=524288,namlen=255,hard,proto=tcp,timeo=600,retrans=2,sec=krb5,mountaddr=192.168.1.219,mountvers=3,mountport=32767,mountproto=tcp,local_lock=none,addr=192.168.1.219 0 0
# time cp -i -arv /mnt/data/tmp/coreboot/src/arch/x86 /mnt/tmp/x86 
cp -i -arv /mnt/data/tmp/coreboot/src/arch/x86 /mnt/tmp/x86  0.01s user
0.07s system 0% cpu 23.294 total

At the same time test with a single file (621M):
* without kerberos: 
cp -i -av /mnt/media/images/GNOME_3.x86_64-0.2.0-Build1.1.iso   0.00s
user 0.69s system 5% cpu 13.521 total
* with kerberos:
cp -i -av /mnt/media/images/GNOME_3.x86_64-0.2.0-Build1.1.iso   0.00s
user 0.55s system 2% cpu 26.299 total

With the same file, but with "dd
if=/mnt/media/images/GNOME_3.x86_64-0.2.0-Build1.1.iso
of=/mnt/tmp/test.iso bs=32M"
gives:
* without kerberos: 651165696 bytes (651 MB) copied, 10.7168 s, 60.8
MB/s
* with kerberos: 651165696 bytes (651 MB) copied, 24.6176 s, 26.5 MB/s


On Tue, 2011-06-07 at 19:07 -0400, J. Bruce Fields wrote:
> On Fri, Jun 03, 2011 at 07:57:16PM +0200, Vladimir Elisseev wrote:
> > There's no mount command involved in timing. It's simply copy of the
> > same directory (with many small files to NFS share with and without
> > sec=krb5 mount option.
> 
> Weird.
> 
> I wonder if the krb5 principal is being mapped to a different user on
> the server side, and that's making some difference.
> 
> Still, could you give us the full details?  (Exactly what commands are
> you running, what results do you see?)
> 
> --b.
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