Hi all. I've got a small question.

What exactly are "wait states"?
When i run 'top' i get the following line:

Cpu(s): 4.9% us, 1.0% sy, 0.0% ni, 83.6% id, 9.8% wa, 0.3% hi, 0.3% si

Now, that's user, system, nice, idle, wait state, hardware interrupts and software interrupts. Right?

Now, it's my understanding that wait states is the amount of time spent waiting for I/O? Is this correct? eg. reading a bunch of data off the disk would cause the wait states to go up?

Well, whenever i do almost anything ( like emerge -uDp world (i have gentoo ), the wait states sit up at about 70-80%, sometimes even higher.

Is this normal? I already have used hdparm to tweak the hd settings. Are they any kernel options(such as ones in /proc) that can help improve this? Or should i consider setting up raid? The PC is used as a desktop and development machine.. not a server, and the disks are only EIDE, not SATA.

Thanks in advance for any help you can give.

Hi, and welcome to LQ!


What are the overall hardware specs, and what does the output of
your tweaked hdparm say?

Also, what throughput does hdparm -tT give you for the devices?


Cheers,
Tink

For an explanation of the columns, see man vmstat: It is perfectly normal for the CPU to spend most of its time "waiting," even when the system is busy as a beaver -- because the CPU is, well, so damned fast.

What you really should be looking for is process wait-states: the things that are causing a particular running program to be delayed involuntarily. Again it is quite normal for processes to do more I/O than anything else, and so to spend most of their time "waiting for I/O." If they are in a swap wait, however, they're being delayed against their will, because of memory constraints.

sundialsvcs:
Well. I would have thought that the computer would spend most of it's time in idle. It's my understanding that while waiting the cpu is blocked g (eg. a synchronized call ), it's not doing anything else.
How then can i find where the bottle neck is to reduce the amount of time processes are waiting? I will say that i almost never swap any memory at all, it's a desktop PC with 1gig memory, so swapping is not an issue. That's why i was asking if upgrading to SATA would reduce the amount of time spent waiting if it's a harddrive bottleneck. I realize the CPU is faster than the seek time of the hard disks, so can i tweak some buffer settings in the kernel or something to help reduce the time spent accessing the disks?

hdb is the only drive worth mentioning, hda is my windows drive and it's put into sleep state at boot.

/dev/hdb:
Timing cached reads: 1488 MB in 2.00 seconds = 743.74 MB/sec
Timing buffered disk reads: 150 MB in 3.04 seconds = 49.33 MB/sec

Here's the info on hdb
/dev/hdb:
multcount = 16 (on)
IO_support = 3 (32-bit w/sync)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 65535/16/63, sectors = 80026361856, start = 0

Model=WDC WD800JB-00JJA0, FwRev=05.01C05, SerialNo=WD-WCAM91538029
Config={ HardSect NotMFM HdSw>15uSec SpinMotCtl Fixed DTR>5Mbs FmtGapReq }
RawCHS=16383/16/63, TrkSize=0, SectSize=0, ECCbytes=66
BuffType=unknown, BuffSize=8192kB, MaxMultSect=16, MultSect=16
CurCHS=16383/16/63, CurSects=16514064, LBA=yes, LBAsects=156301488
IORDY=on/off, tPIO={min:120,w/IORDY:120}, tDMA={min:120,rec:120}
PIO modes: pio0 pio3 pio4
DMA modes: mdma0 mdma1 mdma2
UDMA modes: udma0 udma1 udma2 udma3 udma4 *udma5
AdvancedPM=no WriteCache=enabled
Drive conforms to: device does not report version:

As for overall specs:

P4 2.4(no HT)
1 gig mem(er DDRRAM, just can't remember exact speed)
ASUS P4s533MX motherboard
SIS Chipset

-lspci output
00:00.0 Host bridge: Silicon Integrated Systems [SiS] 651 Host (rev 02)
00:01.0 PCI bridge: Silicon Integrated Systems [SiS] Virtual PCI-to-PCI bridge (AGP)
00:02.0 ISA bridge: Silicon Integrated Systems [SiS] SiS962 [MuTIOL Media IO] (rev 25)
00:02.1 SMBus: Silicon Integrated Systems [SiS] SiS961/2 SMBus Controller
00:02.5 IDE interface: Silicon Integrated Systems [SiS] 5513 [IDE]
00:03.0 USB Controller: Silicon Integrated Systems [SiS] USB 1.0 Controller (rev 0f)
00:03.1 USB Controller: Silicon Integrated Systems [SiS] USB 1.0 Controller (rev 0f)
00:03.3 USB Controller: Silicon Integrated Systems [SiS] USB 2.0 Controller
00:04.0 Ethernet controller: Silicon Integrated Systems [SiS] SiS900 PCI Fast Ethernet (rev 91)
00:10.0 Multimedia audio controller: Creative Labs SB0400 Audigy2 Value
01:00.0 VGA compatible controller: nVidia Corporation NV34 [GeForce FX 5500] (rev a1)


Also, just for some extra info, here's some output from 'dstat' while an updatedb was in progress.