Re: 2.4.8-pre7: still buffer cache problems

[Chris Mason <mason@suse.com>]

On Thursday, August 09, 2001 09:56:31 AM -0400 marc heckmann
<heckmann@hbesoftware.com> wrote:

> Hi.
> 
> While 2.4.8-pre7 definitely fixes the "dd if=/dev/zero of=bigfile bs=1000k
> count=bignumber" case. The "dd if=/dev/hda of=/dev/null" is still quite
> broken for me. while I appreciate that it is a case of "root" doing
> something stupid, it shouldn't mess up the system so badly. On 2.2.19 the
> system is completely useable. on 2.4.8-pre7 it's thrashing swap like mad
> and the buffercache is huge. this is all on a PPC [G3] w/ 192Mb's of RAM
> and 200MB's of swap. so no highmem is involved. vmstat outputs:
>

Hmmm, perhaps its because the buffer cache doesn't have any use-once or
drop behind optimizations?

What happens when you do this instead (assuming your dd supports large
files, otherwise use 1000 instead of 9000)

dd if=/dev/zero of=some_file seek=9000 bs=1MB count=1

Then, run your test again:

dd if=some_file of=/dev/null

-chris