Computer feels slow and laggy

Question

The description is a bit vague, but it's hard to describe the exact problem. I hope I'm posting the correct sub forum.
I'll start with giving all relevant system information I can think of:
root@linux ~ % uname -a
Linux linux 2.6.35-ARCH #1 SMP PREEMPT Wed Sep 29 08:45:18 CEST 2010 x86_64 Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz GenuineIntel GNU/Linux
root@linux ~ % free -m
total used free shared buffers cached
Mem: 2008 1993 15 0 45 1401
-/+ buffers/cache: 546 1462
Swap: 2859 0 2859
root@linux ~ % cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] [raid1]
md0 : active raid1 sda1[0] sdc1[2] sdb1[1]
248896 blocks [3/3] [UUU]
md1 : active raid5 sda2[0] sdc2[2] sdb2[1]
976269824 blocks level 5, 64k chunk, algorithm 2 [3/3] [UUU]
root@linux ~ % uptime
14:03:42 up 3:09, 1 user, load average: 2.62, 1.69, 1.50
root@linux ~ % df -h
Filesystem Size Used Avail Use% Mounted on
udev 10M 164K 9.9M 2% /dev
/dev/lvm/root 19G 8.4G 9.1G 48% /
shm 1005M 0 1005M 0% /dev/shm
/dev/md0 236M 19M 205M 9% /boot
/dev/mapper/lvm-home 896G 796G 55G 94% /home
root@linux ~ % pvdisplay
--- Physical volume ---
PV Name /dev/md1
VG Name lvm
PV Size 931.04 GiB / not usable 512.00 KiB
Allocatable yes (but full)
PE Size 4.00 MiB
Total PE 238347
Free PE 0
Allocated PE 238347
PV UUID ife6Aj-C0ea-JAAP-GcZL-KG3Q-qb5l-rFxkXk
root@linux ~ % vgdisplay
--- Volume group ---
VG Name lvm
System ID
Format lvm2
Metadata Areas 1
Metadata Sequence No 4
VG Access read/write
VG Status resizable
MAX LV 0
Cur LV 3
Open LV 3
Max PV 0
Cur PV 1
Act PV 1
VG Size 931.04 GiB
PE Size 4.00 MiB
Total PE 238347
Alloc PE / Size 238347 / 931.04 GiB
Free PE / Size 0 / 0
VG UUID 5U3AA7-smC5-Fp0T-e0KL-dW3d-D3i7-oesgsz
root@linux ~ % lvdisplay
--- Logical volume ---
LV Name /dev/lvm/root
VG Name lvm
LV UUID gRT6LU-1mdJ-PtK2-dNvX-jnfm-w2St-hv100J
LV Write Access read/write
LV Status available
# open 1
LV Size 18.62 GiB
Current LE 4768
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 254:0
--- Logical volume ---
LV Name /dev/lvm/swap
VG Name lvm
LV UUID ITWVuo-vLZz-dq2C-zXQ5-1058-lisO-sto2Z7
LV Write Access read/write
LV Status available
# open 1
LV Size 2.79 GiB
Current LE 715
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 254:1
--- Logical volume ---
LV Name /dev/lvm/home
VG Name lvm
LV UUID rwSEga-FcS3-jrpV-DzWX-ETpO-03Yh-4X828X
LV Write Access read/write
LV Status available
# open 1
LV Size 909.62 GiB
Current LE 232864
Segments 1
Allocation inherit
Read ahead sectors auto
- currently set to 512
Block device 254:2
+
# OS: Arch Linux x86_64
### Hostname: linux
##### Kernel: 2.6.35-ARCH
###### Uptime: 3:11
; #####; Window Manager: DWM
+##.##### Desktop Environment: None found
+########## Packages: 558
#############; RAM: 548 MB / 2008 MB
###############+ CPU: Intel(R) Core(TM)2 CPU 6600 @ 2.40GHz
####### ####### Shell: Zsh
.######; ;###;`". Root FS: 8.4G / 19G (ext4)
#########. .########`
#' `#
If there is any other system information needed, please don't hesitate to ask.
Now the problem: well it's just general 'latency' and slowness of the computer, affecting nearly all applications. On a fresh boot when I try to login on the TTY I'm able to type half of the password before it gives me the prompt for it. Same when doing a 'su' in a urxvt.
Also, firefox is being very slow and unresponsive. Changing tabs goes slow, even typing text here right now lags from time to time (me typing faster then firefox showing the text). Running applications like SABnzbd makes all things go from bad to worse.
As you probably can understand, working on a computer which is feeling very laggy isn't very amusing. I hope there would be some pointers on how to get it working fast(er).

Answer 1

Thanks for the suggestions so far .
I'm having indeed more then a 1gb free ram and no swap is used, so that's not causing the problem. At the moment that I checked the load to post it over here SABnzbd was actively downloading, so that caused some extra load. But even now, my computer semi-idle (read: only some terminals/firefox) active it still gives me:
20:03:18 up 9:09, 1 user, load average: 0.67, 0.63, 0.72
When I look into (h)top there is no process using excessive amounts of cpu. It seems relative idle, except for firefox popping up from time to time using 10% cpu for half a second. Nothing what should or could cause such a load, so it seems I'm 'affected' by the 2.6.35 bug?
I'm only posting this now because I started to get really annoyed by it (and it might have gotten worse with the .35 bug), but the system is feeling slow for some time now.