Re: NFS3 + kerberos: performance issues

["J. Bruce Fields" <bfields@fieldses.org>]

On Wed, Jun 08, 2011 at 08:26:17AM +0200, Vladimir Elisseev wrote:
> 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

So if I'm reading that right, the client isn't doing any more work, it's
just taking longer, so presumably it's spending more time waiting for
the server.

Might be worth looking at /proc/self/mountstats to see which rpc's are
taking longer.

(Chuck, what's up with the mountstats script?  On a fedora 15 machine
with mountstats installed, it gives me "Statistics for mount point /mnt
not found", but

	# grep mnt /proc/self/mountstats 
	pip1:/exports/ mounted on /mnt with fstype nfs4 statvers=1.0

On a ubuntu machine running the mountstats out of
nfs-utils/tools/mountstats/mountstats.py, it runs without any output.)

Might also be worth looking at vmstat or something on the server.

--b.


> 
> 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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