[Xen-users] Re: Bad performance with SATA disk

[Andres Lagar Cavilla <andreslc@xxxxxxxxxxxxxx>]

Hi there
I'm having exactly the same problem on the same hardware. I used iozone 
to compare disk performance figures, and found that native (i.e. Fedora 
Core 3 kernel 2.6.10-1.770_FC3smp) throughput of the SATA drive 
outperforms xen throughput by a factor of roughly 3.
Logs and config info follow below, I'll gladly attach anything else that 
may be of use.
Help will be greatly appreciated, thanks a bunch.
Andres

lsmod (recompiled dom0 kernel with closely as possible non-xen kernel 
config options):
Module                  Size  Used by
iptable_filter          2304  0
ip_tables              19968  1 iptable_filter
intel_mch_agp           8208  0
agpgart                28072  1 intel_mch_agp
ata_piix                6916  3
libata                 40452  1 ata_piix
aic7xxx               212056  0
sd_mod                 12688  5
scsi_mod               76616  3 libata,aic7xxx,sd_mod

hdparm /dev/sdb:
/dev/sdb:
IO_support   =  0 (default 16-bit)
readonly     =  0 (off)
readahead    = 256 (on)
geometry     = 19452/255/63, sectors = 160000000000, start = 0
Same response under non-xen kernel.

hdparm -d 1 /dev/sdb:
/dev/sdb:
setting using_dma to 1 (on)
HDIO_SET_DMA failed: Inappropriate ioctl for device
However, I get the same response under non-xen kernel.

My lspci and dmesg output are very similar to those of Martti,
lspci | grep SATA:
00:1f.2 IDE interface: Intel Corp. 6300ESB SATA Storage Controller (rev 02)

dmesg:
ata1: SATA max UDMA/133 cmd 0x170 ctl 0x376 bmdma 0xFEA8 irq 15
ata1: dev 0 cfg 49:2f00 82:346b 83:7f01 84:4003 85:3469 86:3e01 87:4003 
88:207f
ata1: dev 0 ATA, max UDMA/133, 78125000 sectors: lba48
ata1: dev 1 cfg 49:2f00 82:3469 83:7f61 84:4003 85:3469 86:3e41 87:4003 
88:207f
ata1: dev 1 ATA, max UDMA/133, 312500000 sectors: lba48
ata1: dev 0 configured for UDMA/133
ata1: dev 1 configured for UDMA/133
scsi2 : ata_piix
 Vendor: ATA       Model: ST340014AS        Rev: 8.05
 Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 78125000 512-byte hdwr sectors (40000 MB)
SCSI device sda: drive cache: write back
SCSI device sda: 78125000 512-byte hdwr sectors (40000 MB)
SCSI device sda: drive cache: write back
sda: sda1 sda2
Attached scsi disk sda at scsi2, channel 0, id 0, lun 0
 Vendor: ATA       Model: WDC WD1600JD-75H  Rev: 08.0
 Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sdb: 312500000 512-byte hdwr sectors (160000 MB)
SCSI device sdb: drive cache: write back
SCSI device sdb: 312500000 512-byte hdwr sectors (160000 MB)
SCSI device sdb: drive cache: write back
sdb: sdb1
Attached scsi disk sdb at scsi2, channel 0, id 1, lun 0


> Hi!
>
>
> I have few Dell PowerEdge 750 servers (each with 4 GB RAM and 250 GB SATA disk)
> in our lab. The disk controllers and the disks are identified like this:
>
>
> # lspci | grep SATA
> 0000:00:1f.2 IDE interface: Intel Corp. 6300ESB SATA Storage Controller (rev 02)
>
>
> ata1: SATA max UDMA/133 cmd 0x170 ctl 0x376 bmdma 0xFEA8 irq 15
> ata1: dev 0 cfg 49:2f00 82:3469 83:7f61 84:4003 85:3469 86:3e41 87:4003 88:207f
> ata1: dev 0 ATA, max UDMA/133, 488281250 sectors: lba48
> ata1: dev 0 configured for UDMA/133
> scsi0 : ata_piix
>  Vendor: ATA       Model: WDC WD2500JD-75H  Rev: 08.0
>  Type:   Direct-Access                      ANSI SCSI revision: 05
> SCSI device sda: 488281250 512-byte hdwr sectors (250000 MB)
> SCSI device sda: drive cache: write back
> SCSI device sda: 488281250 512-byte hdwr sectors (250000 MB)
> SCSI device sda: drive cache: write back
> sda: sda1 sda2 sda3
> Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
>
>
> When running bonnie with the normal Linux 2.6.11 kernel I get numbers like
> these:
>
>
> Version  1.03       ------Sequential Output------ --Sequential Input- 
> --Random-
>                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> xen2             8G 29093  98 56445   6 20761   3 25706  88 53444   3 176.3   0
>                    ------Sequential Create------ --------Random Create--------
>                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                 16  4081  99 +++++ +++ +++++ +++  4125  99 +++++ +++ 12994  99
>
>
> So far so good.
>
>
> If I now I reboot to the Xen domain-0 (Xen 2.0.6 and Linux 2.6.11) and run
> bonnie again (without any active domain-U) I get these numbers:
>
>
> Version  1.03       ------Sequential Output------ --Sequential Input- 
> --Random-
>                    -Per Chr- --Block-- -Rewrite- -Per Chr- --Block-- --Seeks--
> Machine        Size K/sec %CP K/sec %CP K/sec %CP K/sec %CP K/sec %CP  /sec %CP
> xen2             2G  5798  95 50965  53 23156  15  6450  98 55912  16 128.1   1
>                    ------Sequential Create------ --------Random Create--------
>                    -Create-- --Read--- -Delete-- -Create-- --Read--- -Delete--
>              files  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP  /sec %CP
>                 16   664  99 +++++ +++ +++++ +++   676  99 +++++ +++  2699  99
>
>
> Now, the block output and input seem to be almost same. However, "Per Chr" 
> and
> sequential and random file creation are very slow compared to the normal Linux
> kernel. The disk should still be in UDMA/133 mode with domain-0:
>
>
> ata1: SATA max UDMA/133 cmd 0x170 ctl 0x376 bmdma 0xFEA8 irq 15
> ata1: dev 0 cfg 49:2f00 82:3469 83:7f61 84:4003 85:3469 86:3e41 87:4003 88:207f
> ata1: dev 0 ATA, max UDMA/133, 488281250 sectors: lba48
> ata1: dev 0 configured for UDMA/133
> scsi0 : ata_piix
>  Vendor: ATA       Model: WDC WD2500JD-75H  Rev: 08.0
>  Type:   Direct-Access                      ANSI SCSI revision: 05
>
>
> Any ideas why this difference is so huge with domain-0?
>
>
> Martti
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