[SOLVED] High CPU usage during disk IO? Is this normal?

epsilon72 · 02-23-2010, 07:58 PM

I have two pc's that I've recently converted to Debian Lenny boxes, and I've noticed that whenever there's a lot of disk IO, one of my cores (both pc's have dual core cpu's) jumps to 100%. Is this normal? They're both x86_64, and I think both of them should be using the AHCI SATA driver.

If you need any more information about my setup, let me know.

This is the lspci for one of the computers:

Code:

00:00.0 Host bridge: Intel Corporation Mobile PM965/GM965/GL960 Memory Controller Hub (rev 0c)
00:01.0 PCI bridge: Intel Corporation Mobile PM965/GM965/GL960 PCI Express Root Port (rev 0c)
00:1a.0 USB Controller: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #4 (rev 02)
00:1a.1 USB Controller: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #5 (rev 02)
00:1a.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #2 (rev 02)
00:1b.0 Audio device: Intel Corporation 82801H (ICH8 Family) HD Audio Controller (rev 02)
00:1c.0 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 1 (rev 02)
00:1c.1 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 2 (rev 02)
00:1c.3 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 4 (rev 02)
00:1c.5 PCI bridge: Intel Corporation 82801H (ICH8 Family) PCI Express Port 6 (rev 02)
00:1d.0 USB Controller: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #1 (rev 02)
00:1d.1 USB Controller: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #2 (rev 02)
00:1d.2 USB Controller: Intel Corporation 82801H (ICH8 Family) USB UHCI Controller #3 (rev 02)
00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 (rev 02)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev f2)
00:1f.0 ISA bridge: Intel Corporation 82801HEM (ICH8M) LPC Interface Controller (rev 02)
00:1f.1 IDE interface: Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) IDE Controller (rev 02)
00:1f.2 SATA controller: Intel Corporation 82801HBM/HEM (ICH8M/ICH8M-E) SATA AHCI Controller (rev 02)
00:1f.3 SMBus: Intel Corporation 82801H (ICH8 Family) SMBus Controller (rev 02)
01:00.0 VGA compatible controller: nVidia Corporation GeForce 8400M GS (rev a1)
03:01.0 FireWire (IEEE 1394): Ricoh Co Ltd R5C832 IEEE 1394 Controller (rev 05)
03:01.1 SD Host controller: Ricoh Co Ltd R5C822 SD/SDIO/MMC/MS/MSPro Host Adapter (rev 22)
03:01.2 System peripheral: Ricoh Co Ltd R5C843 MMC Host Controller (rev 12)
03:01.3 System peripheral: Ricoh Co Ltd R5C592 Memory Stick Bus Host Adapter (rev 12)
03:01.4 System peripheral: Ricoh Co Ltd xD-Picture Card Controller (rev ff)
09:00.0 Ethernet controller: Broadcom Corporation NetLink BCM5906M Fast Ethernet PCI Express (rev 02)
0c:00.0 Network controller: Intel Corporation PRO/Wireless 3945ABG [Golan] Network Connection (rev 02)

Both are on the default lenny kernel:

Code:

2.6.26-2-amd64

Alex_Dc · 02-23-2010, 09:01 PM

How long is this "jump"? If we are talking only for a few seconds or the extent of the process, than this is perfectly normal.

epsilon72 · 02-23-2010, 09:15 PM

Quote:

Originally Posted by Alex_Dc

How long is this "jump"? If we are talking only for a few seconds or the extent of the process, than this is perfectly normal.

Well, it's as long as the disk access is going - it depends on the application. One time I definitley notice it is during file copying - that shouldn't take too much cpu right?

During those times top doesn't show any process eating cpu, but gnome system monitor shows high usage.

Alex_Dc · 02-23-2010, 09:21 PM

Perfectly normal. It isn't a question of "how much cpu" the process takes, every process will take full advantage of the processing power available to it, i.e. max out your processor. You want this, it is a good thing. There's no reason to get a fast processor if you aren't going to make full use of it.

Edit: Wikipedia will explain this more fully and better than I can in a forum post.

epsilon72 · 02-23-2010, 09:26 PM

Ah okay, Thanks

I looked at the color in gnome system monitor and what I'm seeing is "IOWait". If that's the way it's supposed to be then that's fine - I guess I'm still learning things every day even though I've been using linux for about three years now

H_TeXMeX_H · 02-24-2010, 07:58 AM

Quote:

Originally Posted by epsilon72

Well, it's as long as the disk access is going - it depends on the application. One time I definitley notice it is during file copying - that shouldn't take too much cpu right?

During those times top doesn't show any process eating cpu, but gnome system monitor shows high usage.

Well, during file copying I don't get very much CPU usage at all, certainly not anywhere near 100% on any core. I get around 10 - 15 % usage total, so about 1-4 % per core of 4 cores, again nowhere near 100% of any one core.

What filesystem are you using ? Did you try doing this from the command line ? does it do the same thing ?

I wouldn't be so quick to mark things as solved, unless you are completely convinced they are solved.