SATA performance drop in 2.6.7

[Holger Kiehl]

Hello

Anybody noticed that with 2.6.7 the performance of SATA disks
drops drastically. Right after a boot I get the following with
hdparm:

 Timing buffer-cache reads:   3724 MB in  2.00 seconds = 1861.35 MB/sec
 Timing buffered disk reads:  166 MB in  3.03 seconds =  54.72 MB/sec

It then starts to degrate rapidly:

 Timing buffer-cache reads:   2560 MB in  2.00 seconds = 1280.19 MB/sec
 Timing buffered disk reads:  166 MB in  3.01 seconds =  55.14 MB/sec

 Timing buffer-cache reads:   2164 MB in  2.00 seconds = 1081.08 MB/sec
 Timing buffered disk reads:  166 MB in  3.02 seconds =  55.05 MB/sec

 Timing buffer-cache reads:   1700 MB in  2.00 seconds = 850.13 MB/sec
 Timing buffered disk reads:  146 MB in  3.04 seconds =  48.07 MB/sec

Then about 3 minutes after boot it stays at approx.

  Timing buffer-cache reads:   780 MB in  2.00 seconds = 389.67 MB/sec
  Timing buffered disk reads:  102 MB in  3.01 seconds =  33.89 MB/sec

Controller is a Intel ICH5R and disk is Seagate ST380013AS. With kernel
2.6.6 this does not happen. On another PATA system with 2.6.7 this
does not happen, so I assume the problem must be with SATA.

Holger

PS: Please CC me since I am not subscribed.
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