Re: poor sata performance on 2.6

[cira <linux@spishack.com>]

Denis Vlasenko wrote:
> On Friday 16 April 2004 04:05, Jeff Garzik wrote:

>>It seems like the situation is already resolved, to me.
>>
>>When you mount a filesystem, it changes the default block size (512 or
>>1024) to the filesystem block size, normally 4096.  This would certainly
>>increase the throughput.
> 
> 
> Yes, this works.
> 
> But if one uses unpartitioned disk, why does (s)he need to
> do some blocksize tricks before hdparm starts to measure good performance?
> I think that in this case block layer can coalesce small read requests
> into large ones regardless of block size.

debian unstable
kernel 2.6.5 with udev
promise sata150 tx4
dual seagate ST3120026AS (120GB)
libata 1.02
sata_promise 0.91

Thank you all!

I use lvm2 with /dev/sda and /dev/sdb as members of my volume group. 
That means, no partition tables.  The logical volume contains a 
ReiserFS.  Once the logical volume is mounted the higher transfer rates 
are seen.

22 root@chaljin:/mnt # mount /dev/sdb1 sdb1
23 root@chaljin:/mnt # mount | grep sdb

/dev/scsi/host1/bus0/target0/lun0/part1 on /mnt/sdb1 type ext2 (rw)

24 root@chaljin:/mnt # hdparm -t /dev/sdb

/dev/sdb:
  Timing buffered disk reads:   32 MB in  3.04 seconds =  10.52 MB/sec

25 root@chaljin:/mnt # hdparm -t /dev/sdb

/dev/sdb:
  Timing buffered disk reads:  166 MB in  3.02 seconds =  54.98 MB/sec

26 root@chaljin:/mnt # umount /dev/sdb1

Ah, the change is not stable either.  If I umount the partition it
reverts to the slower rate.  There is no need to reboot.

 > Konstantin, does dd give you the same behaviour as hdparm?
 > --
 > vda

Yes, dd does behave the same as hdparm.

39 root@chaljin:/root # dd bs=512 count=65536 if=/dev/sdb of=/dev/null

65536+0 records in
65536+0 records out
33554432 bytes transferred in 3.203750 seconds (10473487 bytes/sec)

40 root@chaljin:/root # cd /mnt
41 root@chaljin:/mnt # mount /dev/sdb1 sdb1
42 root@chaljin:/mnt # dd bs=512 count=65536 if=/dev/sdb of=/dev/null

65536+0 records in
65536+0 records out
33554432 bytes transferred in 3.184339 seconds (10537330 bytes/sec)

43 root@chaljin:/mnt # dd bs=512 count=65536 if=/dev/sdb of=/dev/null

65536+0 records in
65536+0 records out
33554432 bytes transferred in 0.400394 seconds (83803552 bytes/sec)

44 root@chaljin:/mnt # dd bs=512 count=339968 if=/dev/sdb of=/dev/null

339968+0 records in
339968+0 records out
174063616 bytes transferred in 2.705558 seconds (64335569 bytes/sec)

45 root@chaljin:/mnt #

If anyone wants further testing just let me know.  I still have one 
blank disk and one promise sata150 tx4 controller that is not yet in use.

-cira

(I'm on the linux-ide list)