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SubjectRe: 2.4 disk speed 66% slowdown...
Date
Linda Walsh wrote:
> I think we're on to something. I did gen's of the kernel with
[snip]
> The REAL problem was in disk performance. The apm made no difference:
>
> hdparm -t /dev/hda1 /dev/hda3 /dev/hda4 /dev/hda5 /dev/hda7
> 1) 2.2.17
> /dev/hda1: Timing buffered disk reads: 64 MB in 4.76 seconds = 13.45 MB/sec
> /dev/hda3: Timing buffered disk reads: 64 MB in 4.57 seconds = 14.00 MB/sec
> /dev/hda4: Timing buffered disk reads: 64 MB in 6.47 seconds = 9.89 MB/sec
> /dev/hda5: Timing buffered disk reads: 64 MB in 5.08 seconds = 12.60 MB/sec
> /dev/hda7: Timing buffered disk reads: 64 MB in 5.10 seconds = 12.55 MB/sec
>
> 2) 2.4 w/apm
> /dev/hda1: Timing buffered disk reads: 64 MB in 16.03 seconds = 3.99 MB/sec
> /dev/hda3: Timing buffered disk reads: 64 MB in 15.87 seconds = 4.03 MB/sec
> /dev/hda4: Timing buffered disk reads: 64 MB in 15.67 seconds = 4.08 MB/sec
> /dev/hda5: Timing buffered disk reads: 64 MB in 15.82 seconds = 4.05 MB/sec
> /dev/hda7: Timing buffered disk reads: 64 MB in 15.85 seconds = 4.04 MB/sec
[snip]

Your slowdown's different from mine, then. hdparm gives me 16.5 MB/sec
(or so) for both 2.2 & 2.4 (with APM in both cases). I must stress that
I haven't tried 2.4.0 or 2.4.1pre on my Inspiron 5000e yet, so I don't
even know if the problem that caused my slowdown still exists.

(Just to clarify my case: 750MHz Pentium III, 256MB RAM, 32GB IBM HD,
Intel 440BX chipset. If you need more data, I'll collect it when I get a
chance, but I'd be surprised if 2.4.1 doesn't come out first.)

While I'm writing this email, I may as well mention that I have a problem
with booting my Inspiron 5000e under 2.4 (all of my actual 2.4test usage
on that machines has been with Slackware 7.1's Disc 2 and the
corresponding rootdisk). That machine has Red Hat 7.0 installed on an ext2
disk image file, stored on a vfat partition and loop mounted. (Actually,
/usr and a subdirectory of /home are each on different image files now,
for 3 total, but booting never gets far enough for that to be relevant.)

The RAM disk I use for booting off the hard drive is the default one set
up by the Red Hat 7 installer, except there are no modules on it (I
compile in everything that's needed for booting) and the last line of
linuxrc has an echo statement. After that echo statement runs, I get the
following error message under 2.4.0, but not 2.2.1[678]: (from memory, so
the exact message might be slightly different)

panic: I have no root and I must scream

If I comment out that panic, I get some rather interestng messages, but I
don't remember any of them. I wasn't planning on reporting this until I
got a chance to put together a self-contained package & instructions for
reproducing the problem, but since I'm writing an email to the list, here
it is...

-Barry K. Nathan <barryn@pobox.com>
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