Re: kernel freeze

From: Martin J. Bligh (mbligh@aracnet.com)
Date: Tue Nov 05 2002 - 02:50:21 EST


>> I'll lay you a large bet that lowmem is full of garbage.
>> Probably buffer_heads, inodes or PTEs. Output of /proc/meminfo
>> and /proc/slabinfo as you approach oblivion would be useful.
>> As would a description of the workload that triggers it.
>>
>> M.
> I think it's the reason. But I have to decreased memory from 4G to 2G
> because of the complain from my customers, so I can't give you the
> /proc/meminfo or /proc/slabinfo now. :(

The patches don't seem to have wended their way back to mainline
yet, probably because people have been concentrating on 2.5 recently.
I think Andrea's -aa kernel has fixes for most, if not all of these
problems.

> Why the linux-vm can't manage lowmem correctly? I have seen some
> articles talking about the LRU pre zone patch, but why 2.4.19+rmap14a
> patch also has this problem?

rmap won't help you in this instance, as the stuff you're filling
ZONE_NORMAL with is unswappable. In fact, it may make it worse,
due the overhead of pte_chains ... but this will probably only
hurt you if you have many large tasks sharing memory.

Changing PAGE_OFFSET from 3Gb to 2Gb may be a better workaround than
decreasing from 4Gb to 2Gb of RAM, if you don't have any huge single
process.

M.

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