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Altera_Forum's avatar
Altera_Forum
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16 years ago

Has anyone encountered this error before?

Hello folks, I am getting this error frequently when testing an application on the DE2 and uClinux. It happens when calling a command . In my case, it happens with ftpput, which is the one I am...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
16 years ago

If you're using a 2.6.30 kernel (not sure when it first appeared), the default kernel config contains:

(1) Turn on mmap() excess space trimming before booting

You should set this to 0 to help prevent memory fragmentation.

This setting is also at /proc/sys/vm/nr_trim_pages.

Besides that, since kernel 2.6.27 (where I started on my nios2 project), I've been seeing that no matter what, over time, jffs2's write cache seems to cause memory fragmentation. I believe the memory that seems to be getting stuck is seen in /proc/meminfo as Unreclaimable.

Instead of just looking at /proc/meminfo, you should also keep an eye on /proc/buddyinfo.

/> cat /proc/buddyinfo

Node 0, zone DMA 37 13 9 3 1 1 2 2 0 0 0 0 0 0

That says there are 37 4KB pages available, 13 8KB pages available, 9 16KB pages available, 3 32KB pages available, etc.