Performance

Tests based on LTSP 20.3+ under Debian 10.

Test hardware

Server

Virtual Machine using KVM with 32 CPU threads and 50GB RAM.

The Server runs Debian Buster has a 10Gbit/s link to a HP Procurve Managed Switch in which all thin clients connect to via 1Gbit/s connections.

Client

Motherboard	Shuttle DS77U
CPU	i3-7100
RAM	8GB
NIC	1Gbit/s

Compression & Copying to RAM tests

Test performance after grub and kernel messages there is a blank screen, these measurements are taken from the time the blank screen appears till the time I’m at the GUI login screen.

	Time
LTSP 20.3	33s
disable nfs-server & add firmware-realtek	30s
lzo image	28s
xz image	45s
zstd image	25s
dd to RAM in pre_initrd & zstd image	5s
image to ram	broken

Libreoffice 6.3 starting

	Cold	Warm
Initially LTSP 20.1	15s	3s
LTSP 20.3	9s	2s
dd to RAM in pre_initrd	9s	2s
dd to RAM in pre_initrd & zstd image	4s	1.5s
image to ram	broken

Setup ‘dd to RAM in pre_initrd’

Create config

install -m 0660 -g sudo /usr/share/ltsp/common/ltsp/ltsp.conf /etc/ltsp/ltsp.conf

Add to /etc/ltsp/ltsp.conf [clients] section

PRE_INITRD_BOTTOM_IMAGE_TO_RAM="dd if=/root/images/x86_64.img of=/dev/null &"

Update settings

ltsp initrd

Emacs starting

I found that most applications started very fast once I used ‘dd to RAM’. Applications like libreoffice and firefox started within a few seconds. However applications which required a lot of files to be loaded took longer than usual. Emacs and git were two of these programs.

I ran a number of tests using different ways to mount the file system and here are the results I found;

Test Environment

debian10-ltsp	Debian 10
old LTSP	Debian 8
emacs version	26.1
files in emacs config	79MB 4846files
files in agenda	435MB 1538files

Performance Test Results

	Start	Agenda	Agenda
	secs	cold	warm
Fat-client NFSv3 -> debian10-ltsp NFSv3 -> old LTSP	105	103
debian10-ltsp VM direct NFSv3 -> old LTSP	18	61
debian10-ltsp VM direct w/local files	3	40	6
Fat-client NFSv3 -> debian10-ltsp w/local files	15	37	5
Fat-client NFSv4 -> debian10-ltsp w/local files	14	43	5
Fat-client NFSv4.2 -> debian10-ltsp w/local files	13	36	5
Fat-client NFSv4.2 -> LTSPHOST “metal”	11	46	5
Fat-client NFSv4.2 -> old LTSP	20	56	5
Fat-client ssh -X -> debian10-ltsp to emacs	4	39	6
Fat-client Samba -> debian10-ltsp w/local files	49	162	6
Fat-client SSHFS -> debian10-ltsp w/local files	27	157	5
old LTSP VM direct w/local files	4	42
Thin client -> old LTSP VM w/local files	4	40	6

Mounting as NFS4.2

/etc/ltsp/ltsp.conf

FSTAB_HOME="server:/home /home nfs4 nfsvers=4.2,defaults,nolock 0 0"

Setting different rsize & wsize

• [X] Test different rsize values = no real difference

  rsize		Start	Agenda	Agenda
  & wsize		secs	cold	warm
  1048576	1M	13	36	5
  4096	4k	13	37	5
  8192	8k
  16384	16k
  32768	32k
  65536	64k	15	37	5

  NOTE: Default it’s 1048576 The general idea here is the larger the number the better for streaming, whilst the lower the number the better for random reads.

  Setting it to 4k

  FSTAB_HOME="server:/home /home nfs4 nfsvers=4.2,rsize=4096,defaults,nolock 0 0"
      

Conclusion

No real difference so keep using the default.