On Mon, Dec 10, 2001 at 11:57:08PM -0800, H . J . Lu wrote:
> On Mon, Dec 10, 2001 at 08:34:52PM -0800, H . J . Lu wrote:
> > I have a very strange problem. The disk I/O of my QPS M3 80GB HD is
> > very slow under 2.4.10 and above. I got like 1.77 MB/s from hdparm.
> > But under 2.4.9, I got 14 MB/s on the same hardware. A 30GB HD has
> > consistent I/O performance under 2.4.9 and above on the same bus. Has
> > anyone else seen this? Does anyone have a large (>= 80GB) 1394 HD?
> >
>
> I did a binary search. 2.4.10-pre10 is the last good kernel. I got
>
> # hdparm -t /dev/sda
>
> /dev/sda:
> Timing buffered disk reads: 64 MB in 4.40 seconds = 14.55 MB/sec
>
> Even since 2.4.10-pre11 up to 2.4.16, I got about 1.77 MB/sec on the
> same hardware. However, I don't have problems with 80GB IDE HD. Has
> anyone seen I/O problems on large (>= 80GB) SCSI HD or HD with SCSI
> emulation?
I tracked own the problem to 40_blkdev-pagecache-17 in the 2.4.10
pre10aa1 patch. When it is applied, the disk I/O on some drives become
very slow. It not only happens to my 80GB 1394 HD, but also the second
IDE drive. Before the patch
# hdparm -t /dev/hdd
/dev/hdd:
Timing buffered disk reads: 64 MB in 8.02 seconds = 7.98 MB/sec
After the patch
# hdparm -t /dev/hdd
/dev/hdd:
Timing buffered disk reads: 64 MB in 21.09 seconds = 3.03 MB/sec
The slow down is not as bad as 1394. But it is still very significant.
I couldn't figure out why it only affects certain drives.
H.J.
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This archive was generated by hypermail 2b29 : Sat Dec 15 2001 - 21:00:22 EST