cpu consumption

cpu consumption

[Raz Ben-Jehuda(caro)]

Hello Jeff.
Here is my problem.

When I issue a READ operation over a SATA disk in linux i have
huge cpu consumption , about 90% cpu usage.

I am using MAXTOR disks in a supermicro machine.
the cpu test was made when i "raw read" from the DISK using DIRECT_IO.

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

this is my dmesg.
ata1: SATA max UDMA/133 cmd 0xE900 ctl 0xEA02 bmdma 0xED00 irq 10
ata2: SATA max UDMA/133 cmd 0xEB00 ctl 0xEC02 bmdma 0xED08 irq 10
ata1: dev 0 cfg 49:2f00 82:7c6b 83:7f09 84:4673 85:7c69 86:3e01 87:4663 88:207f
ata1: dev 0 ATA, max UDMA/133, 490234752 sectors: lba48
ata1: dev 0 configured for UDMA/133
scsi0 : ata_piix
ata2: dev 0 cfg 49:2f00 82:7c6b 83:7f09 84:4673 85:7c69 86:3e01 87:4663 88:207f
ata2: dev 0 ATA, max UDMA/133, 490234752 sectors: lba48
ata2: dev 0 configured for UDMA/133
scsi1 : ata_piix
  Vendor: ATA       Model: Maxtor 7L250S0    Rev: BANC
  Type:   Direct-Access                      ANSI SCSI revision: 05
  Vendor: ATA       Model: Maxtor 7L250S0    Rev: BANC
  Type:   Direct-Access                      ANSI SCSI revision: 05
SCSI device sda: 490234752 512-byte hdwr sectors (251000 MB)
SCSI device sda: drive cache: write back
SCSI device sda: 490234752 512-byte hdwr sectors (251000 MB)
SCSI device sda: drive cache: write back
 /dev/scsi/host0/bus0/target0/lun0: p1 p2
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
SCSI device sdb: 490234752 512-byte hdwr sectors (251000 MB)
SCSI device sdb: drive cache: write back
SCSI device sdb: 490234752 512-byte hdwr sectors (251000 MB)
SCSI device sdb: drive cache: write back
 /dev/scsi/host1/bus0/target0/lun0:
Attached scsi disk sdb at scsi1, channel 0, id 0, lun 0
Attached scsi generic sg0 at scsi0, channel 0, id 0, lun 0,  type 0
Attached scsi generic sg1 at scsi1, channel 0, id 0, lun 0,  type 0
mice: PS/2 mouse device common for all mice
i2c /dev entries driver
md: linear personality registered as nr 1
md: raid0 personality registered as nr 2
md: raid1 personality registered as nr 3
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX


Thank you.
--
Raz

Re: cpu consumption

[Jeff Garzik]

Raz Ben-Jehuda(caro) wrote:
> Hello Jeff.
> Here is my problem.
> 
> When I issue a READ operation over a SATA disk in linux i have
> huge cpu consumption , about 90% cpu usage.
> 
> I am using MAXTOR disks in a supermicro machine.
> the cpu test was made when i "raw read" from the DISK using DIRECT_IO.

I dunno... do some profiling (in-kernel profiler, or oprofile) and see 
where the CPU is being consumed.

Are you also seeing a lot of interrupts?

	Jeff

Re: cpu consumption

[Tejun Heo]

Jeff Garzik wrote:
> Raz Ben-Jehuda(caro) wrote:
> 
>> Hello Jeff.
>> Here is my problem.
>>
>> When I issue a READ operation over a SATA disk in linux i have
>> huge cpu consumption , about 90% cpu usage.
>>
>> I am using MAXTOR disks in a supermicro machine.
>> the cpu test was made when i "raw read" from the DISK using DIRECT_IO.
> 
> 
> I dunno... do some profiling (in-kernel profiler, or oprofile) and see 
> where the CPU is being consumed.
> 
> Are you also seeing a lot of interrupts?
> 
>     Jeff
> 
> 

Jeff, this one is resolved.  It turned out that Raz mistook wait time to 
be busy.

Hmmm... marc doesn't show any mesage after 2005-11-25.  This is is 
resolved in a thread on linux-ide named "CPU usage is very high while 
io'ing a sata disk" from Raz.  The first message of the thread is posted 
on 2005-11-30 06:23 +0900.

-- 
tejun