2.6.18-1.2189.fc5: Decreased data throughput?

[Mostafa Afgani]

Hi,

In order to use the JMicron controller on my Asus P5B, I decided to
try out 2.6.18-1.2189.fc5 kernel from updates-testing. Prior to this I
was stuck running the 2.6.15-1.2054_FC5 kernel due to stability
issues.

For the HDD, I am using the ICH8 sata ports running in AHCI mode. To
test throughput, I ran the following command:

$ dd if=/dev/zero of=/tmp/dummy bs=100k count=10

With the 2054 kernel, I see a throughput of around 500 MB/s. With the
2189, that value is almost half at around 230 MB/s.

I've checked the output of dmesg for both kernels, and apart from the
ahci version and the failure to probe the JMicron controller on 2054,
they are nearly identical:

demsg-2054:
------------------
ahci 0000:00:1f.2: version 1.2
ACPI: PCI Interrupt 0000:00:1f.2[B] -> GSI 19 (level, low) -> IRQ 17
PCI: Setting latency timer of device 0000:00:1f.2 to 64
ahci 0000:00:1f.2: AHCI 0001.0100 32 slots 4 ports ? Gbps 0x33 impl SATA mode
ahci 0000:00:1f.2: flags: 64bit ilck stag led pmp pio
ata1: SATA max UDMA/133 cmd 0xFFFFC2000000C900 ctl 0x0 bmdma 0x0 irq 17
ata2: SATA max UDMA/133 cmd 0xFFFFC2000000C980 ctl 0x0 bmdma 0x0 irq 17
ata3: SATA max UDMA/133 cmd 0xFFFFC2000000CA00 ctl 0x0 bmdma 0x0 irq 17
ata4: SATA max UDMA/133 cmd 0xFFFFC2000000CA80 ctl 0x0 bmdma 0x0 irq 17
ata1: SATA link up 3.0 Gbps (SStatus 123)
ata1: dev 0 cfg 49:2f00 82:746b 83:7f01 84:4023 85:7469 86:3c01 87:4023 88:407f
ata1: dev 0 ATA-7, max UDMA/133, 488397168 sectors: LBA48
ata1: dev 0 configured for UDMA/133
scsi0 : ahci
ata2: SATA link down (SStatus 0)
scsi1 : ahci
ata3: SATA link down (SStatus 0)
scsi2 : ahci
ata4: SATA link down (SStatus 0)
scsi3 : ahci
 Vendor: ATA       Model: WDC WD2500KS-00M  Rev: 02.0
 Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 488397168 512-byte hdwr sectors (250059 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
SCSI device sda: 488397168 512-byte hdwr sectors (250059 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
 sda: sda1 sda2
sd 0:0:0:0: Attached scsi disk sda
ACPI: PCI Interrupt 0000:02:00.0[A] -> GSI 16 (level, low) -> IRQ 16
PCI: Setting latency timer of device 0000:02:00.0 to 64
ahci 0000:02:00.0: AHCI 0001.0000 32 slots 2 ports 3 Gbps 0x3 impl SATA mode
ahci 0000:02:00.0: flags: 64bit ncq pm led clo pmp pio slum part
ata5: SATA max UDMA/133 cmd 0xFFFFC20000028100 ctl 0x0 bmdma 0x0 irq 16
ata6: SATA max UDMA/133 cmd 0xFFFFC20000028180 ctl 0x0 bmdma 0x0 irq 16
ata5: SATA link down (SStatus 0)
scsi4 : ahci
ata6: SATA link down (SStatus 0)
scsi5 : ahci
GSI 18 sharing vector 0xB9 and IRQ 18
ACPI: PCI Interrupt 0000:02:00.1[B] -> GSI 17 (level, low) -> IRQ 18
ahci: probe of 0000:02:00.1 failed with error -12

dmesg-2189:
------------------
ahci 0000:00:1f.2: version 2.0
ACPI: PCI Interrupt 0000:00:1f.2[B] -> GSI 19 (level, low) -> IRQ 177
PCI: Setting latency timer of device 0000:00:1f.2 to 64
ahci 0000:00:1f.2: AHCI 0001.0100 32 slots 4 ports ? Gbps 0x33 impl SATA mode
ahci 0000:00:1f.2: flags: 64bit ilck stag led pmp pio
ata1: SATA max UDMA/133 cmd 0xFFFFC20000026900 ctl 0x0 bmdma 0x0 irq 233
ata2: SATA max UDMA/133 cmd 0xFFFFC20000026980 ctl 0x0 bmdma 0x0 irq 233
ata3: SATA max UDMA/133 cmd 0xFFFFC20000026A00 ctl 0x0 bmdma 0x0 irq 233
ata4: SATA max UDMA/133 cmd 0xFFFFC20000026A80 ctl 0x0 bmdma 0x0 irq 233
scsi0 : ahci
PM: Adding info for No Bus:host0
ata1: SATA link up 3.0 Gbps (SStatus 123 SControl 300)
ata1.00: ATA-7, max UDMA/133, 488397168 sectors: LBA48
ata1.00: ata1: dev 0 multi count 16
ata1.00: configured for UDMA/133
scsi1 : ahci
PM: Adding info for No Bus:host1
ata2: SATA link down (SStatus 0 SControl 300)
scsi2 : ahci
PM: Adding info for No Bus:host2
ata3: SATA link down (SStatus 0 SControl 0)
scsi3 : ahci
PM: Adding info for No Bus:host3
ata4: SATA link down (SStatus 0 SControl 0)
PM: Adding info for No Bus:target0:0:0
 Vendor: ATA       Model: WDC WD2500KS-00M  Rev: 02.0
 Type:   Direct-Access                      ANSI SCSI revision: 05
PM: Adding info for scsi:0:0:0:0
SCSI device sda: 488397168 512-byte hdwr sectors (250059 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
SCSI device sda: 488397168 512-byte hdwr sectors (250059 MB)
sda: Write Protect is off
sda: Mode Sense: 00 3a 00 00
SCSI device sda: drive cache: write back
 sda: sda1 sda2
sd 0:0:0:0: Attached scsi disk sda
ACPI: PCI Interrupt 0000:02:00.0[A] -> GSI 16 (level, low) -> IRQ 169
PCI: Setting latency timer of device 0000:02:00.0 to 64
ahci 0000:02:00.0: AHCI 0001.0000 32 slots 2 ports 3 Gbps 0x3 impl SATA mode
ahci 0000:02:00.0: flags: 64bit ncq pm led clo pmp pio slum part
ata5: SATA max UDMA/133 cmd 0xFFFFC20000028100 ctl 0x0 bmdma 0x0 irq 169
ata6: SATA max UDMA/133 cmd 0xFFFFC20000028180 ctl 0x0 bmdma 0x0 irq 169
scsi4 : ahci
PM: Adding info for No Bus:host4
ata5: SATA link down (SStatus 0 SControl 300)
scsi5 : ahci
PM: Adding info for No Bus:host5
ata6: SATA link down (SStatus 0 SControl 300)


Regards,
Mostafa