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GODLiKE
n00b
Joined: 11 Jan 2007
Posts: 62
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 Posted: Sat May 05, 2007 7:08 pm Post subject: High CPU Usage on DMA drive? |
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Hi, I'm currently using the 2.6.19-gentoo-r5 sources for a home server. I used to have w2k3 but after a little while I moved to Gentoo (my main system on my PC is also Gentoo).
I noticed from the beginning that Samba transfers were really slow (4/5/6 (6 if I get lucky) MB/sec on a 100mbps LAN), so I started using FTP, which was a little better but not where it should be. I also noticed that when transferring, CPU usage went through the roof, stuck at 100%, both with Samba and FTP.
The disk is a 7200RPM 80GB Seagate Barracuda, using a 40pin ATA cable, on a Soyo 7VBA motherboard, with a P3 633MHz and 512MB. I have (or at least I guess I have) the necessary drivers compiled in the kernel
| Code: | <*> ATA/ATAPI/MFM/RLL support
<*> Enhanced IDE/MFM/RLL disk/cdrom/tape/floppy support
<*> Include IDE/ATA-2 DISK support
[*] Use multi-mode by default
<*> Include IDE/ATAPI CDROM support
<*> generic/default IDE chipset support
[*] CMD640 chipset bugfix/support
[*] PCI IDE chipset support
[*] Sharing PCI IDE interrupts support
<*> Generic PCI IDE Chipset Support
<*> RZ1000 chipset bugfix/support
[*] Generic PCI bus-master DMA support
[*] Use PCI DMA by default when available
<*> VIA82CXXX chipset support |
Those are all the options under ATA/ATAPI/MFM/RLL support. I used to have enabled the new SATA support (for PATA & stuff) section but disabled it as I'm not sure which one of them (the normal ATA or the new SATA) to use (anyways, I've made some reading and the drive shows up as hda so I guess the ATA section is the one that recognizes the drive).
To my surprise, DMA is enabled on the disk
| Code: | tanya linux # hdparm /dev/hda
/dev/hda:
multcount = 16 (on)
IO_support = 1 (32-bit)
unmaskirq = 1 (on)
using_dma = 1 (on)
keepsettings = 0 (off)
readonly = 0 (off)
readahead = 256 (on)
geometry = 65535/16/63, sectors = 156301488, start = 0
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And this is the speed test
| Code: | tanya linux # hdparm -tT /dev/hda
/dev/hda:
Timing cached reads: 400 MB in 2.02 seconds = 198.44 MB/sec
Timing buffered disk reads: 52 MB in 3.01 seconds = 17.28 MB/sec
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Of course, CPU Usage during the hdparm test went through the roof too.
I don't know if those values are OK, but I keep getting 100% cpu usage.
I believe I have something wrong on the kernel config, as I have this same kernel on my PC (which is a DFI Lanparty NF4 with a SATA2 7200RPM 320GB Seagate disk) and I also get 100% cpu usage when using the disk, but this later issue is subject for another thread and not this one  . I'm mainly worried about my server issue, and I'll worry about my PC issue later.
Any help would be appreciated.
Thanks in advance!
EDIT: forgot to mention CPU and Memory.
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GERÓNIMOOOOOOOOOOOOOOOOOOOO!!! |
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Keruskerfuerst
Advocate
Joined: 01 Feb 2006
Posts: 2289
Location: near Augsburg, Germany
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| Posted: Sat May 05, 2007 8:50 pm Post subject: |
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To find out, which chipset your computer is using, just use
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GODLiKE
n00b
Joined: 11 Jan 2007
Posts: 62
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| Posted: Sat May 05, 2007 9:11 pm Post subject: |
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| Keruskerfuerst wrote: | To find out, which chipset your computer is using, just use
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I know which chipset it uses, it's the VIA VT82Cxxxx, and I have it configured on the kernel as you can see from above.
Another thing I forgot to mention is that neither top nor ps show any cpu-eating process during disk i/o usage (when CPU % explodes), and that this also happens when deleting files (which takes longer than usual).
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GODLiKE
n00b
Joined: 11 Jan 2007
Posts: 62
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| Posted: Tue May 08, 2007 1:17 pm Post subject: |
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Sorry for the bump. I have been reading this and although it is not explicitly the same chipset as mine (I have a VT82C686 southbridge), I was told by a close friend of mine (who happens to be a hardware reviewer) that my chipset is known to have a serious DMA issue which was worked-around on the Windows drivers (but I would not expect the work-around to be on the Linux drivers though). So I think I better buy an Intel i85 based motherboard before something like this happens to my server  .
If anyone had any similar experiences with the VIA VT82C686 southbridge chipset, I'd appreciate if you would share it here.
Thanks again.
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