lkml.org 
[lkml]   [2006]   [Oct]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
Subjectloading EHCI_HCD slows down IDE disk performance by 50%
Quite a while ago I filed

https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=188630

as it looked like moving from FC3 to FC5 caused a 40%
drop in IDE disk performance.

After finally finding (a LOT of) time to dig into the issue,
turns out it's a kernel problem that currently can be
described as a 50% performance hit for IDE disks, and
that only shows up when loading the USB2.0 ehci_hcd
module (I originally didn't have an external USB2.0 disk
and bought it at the same time I moved from FC3 to FC5).


The problem traces back at least to 2.6.16-rc5-git8, which
was the kernel du jour at the time I originally reported
the issue on lkml:

http://www.ussg.iu.edu/hypermail/linux/kernel/0604.1/0046.html

and is still present in 2.6.19-rc3-git4 (running both FC3
and FC5) and the current FC6 kernel.

Unfortunately, the uhci_hcd module which also can
speak to my external USB2.0 disk is too slow to be used
in place of ehci_hcd... like this:

[root@donkey ~]# uname -a
Linux donkey 2.6.18-1.2798.fc6 #1 SMP Mon Oct 16 14:37:32 EDT 2006
i686 athlon i386 GNU/Linux
[root@donkey ~]# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 66 MB in 3.06 seconds = 21.56 MB/sec
[root@donkey ~]# hdparm -t /dev/sda

/dev/sda:
Timing buffered disk reads: 68 MB in 3.07 seconds = 22.18 MB/sec

<okay, replace ehci_hcd with uhci_hcd...>

[root@donkey ~]# modprobe -r ehci_hcd; modprobe uhci_hcd

<and yes, we have full speed back from the IDE disk...>

[root@donkey ~]# hdparm -t /dev/hda

/dev/hda:
Timing buffered disk reads: 120 MB in 3.04 seconds = 39.51 MB/sec

<...but the USB2.0 external disk gets a 20x hit performance-wise>

[root@donkey ~]# hdparm -t /dev/sda

/dev/sda:
Timing buffered disk reads: 4 MB in 4.18 seconds = 980.44 kB/sec


Machine is a K7-800 with 512MB RAM, two internal 160GB
IDE disks, an external 250GB USB2.0 disk, IDE DVD burner.

From my dmesg under the FC6 kernel:

VP_IDE: chipset revision 16
VP_IDE: not 100% native mode: will probe irqs later
VP_IDE: VIA vt82c686a (rev 22) IDE UDMA66 controller on pci0000:00:07.1
ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda:DMA, hdb:DMA
ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc:DMA, hdd:pio
Probing IDE interface ide0...
hda: SAMSUNG SP1604N, ATA DISK drive
hdb: Maxtor 6Y160P0, ATA DISK drive
ide0 at 0x1f0-0x1f7,0x3f6 on irq 14
Probing IDE interface ide1...
hdc: TSSTcorpCD/DVDW TS-H552B, ATAPI CD/DVD-ROM drive
ide1 at 0x170-0x177,0x376 on irq 15
hda: max request size: 512KiB
hda: 312581808 sectors (160041 MB) w/2048KiB Cache, CHS=19457/255/63, UDMA(66)
hda: cache flushes supported
hda: hda1 hda2 hda3 hda4 < hda5 hda6 >
hdb: max request size: 512KiB
hdb: 320173056 sectors (163928 MB) w/7936KiB Cache, CHS=19929/255/63, UDMA(66)
hdb: cache flushes supported

...and...

usb 5-4: new high speed USB device using ehci_hcd and address 2
usb 5-4: configuration #1 chosen from 1 choice
SCSI subsystem initialized
Initializing USB Mass Storage driver...
scsi0 : SCSI emulation for USB Mass Storage devices
usbcore: registered new driver usb-storage
USB Mass Storage support registered.
usb-storage: device found at 2
usb-storage: waiting for device to settle before scanning
Vendor: ST325082 Model: 3A Rev: 0 0
Type: Direct-Access ANSI SCSI revision: 00
usb-storage: device scan complete


Any hints/tips about what to try with this issue will be
of course very welcome.

Thanks in advance, ciao,

--alessandro

"...when I get it, I _get_ it"

(Lara Eidemiller)
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-10-29 19:17    [W:0.042 / U:0.496 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site