[Bug 384680] [NEW] Slow when large amount of memory used, even if plenty left

[John McCabe-Dansted]

Public bug reported:

Binary package hint: linux-image

If I run "sudo memtester 3600" on a 4GiB machine, the system becomes
unusably slow and the hard disk is being continually accessed, even when
I am doing nothing and have only two epiphany windows open (and
memtester).

Expected behaviour:
Since there is over 384MB of memory leftover from memtester, and Ubuntu is fast with 384MB if you only have a couple of couple of windows open, I would expect Ubuntu to be fast and responsive after paging out unneeded memory.

Actual behaviour:
The next morning Ubuntu is still slow, having had plenty of time to rearrange its memory use and page out unneed data. Epiphany reports that there is an unresponsive script on Gmail. The harddisk is constantly active, even when not doing anything.

Allocating 3600MB of RAM with memtester is a rather pathological case.
However I have had severe slow downs when opening two VMs with less than
512MiB each on a 2GiB machine (leaving over 1GiB to other processes), so
similar problems can occur in reasonable everyday usage. Tested on 9.04
64bit with a Dual Core 2 processor.

** Affects: linux-meta (Ubuntu)
     Importance: Undecided
         Status: New

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Slow when large amount of memory used, even if plenty left
https://bugs.launchpad.net/bugs/384680
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