Re: hints at modifying kswapd params in 2.4.16

[Sven Heinicke <sven@research.nj.nec.com>]

Does the AC kernel still have the old VM?  I really wanna stick the
the new stuff but but a need a stable system.  Older kernels 2.4.8 had
highmem issues, not the 2.4.16 has kswap issues.

Ken Brownfield writes:
 > Yes, 2.4.16 fixed a major source of kswapd thrashing for (at least)
 > mmapped memory, but there are still some corner cases left which I've
 > also seen.  For instance, in the new case I'm seeing kswapd thrashing
 > even when freepages hasn't been reached under heavy I/O.  I'm under the
 > impression that this behavior is more of a mis-behavior rather than a
 > mis-tuning.
 > 
 > I don't think I've seen a response to my recent post go by; hopefully
 > the VM issues can still be debugged soon even after the handoff to
 > Marcelo... :-)
 > -- 
 > Ken.
 > brownfld@irridia.com
 > 
 > PS: The hardware in question on my end is an HP LH6000r, 6-way Xeon, 4GB.
 > 
 > On Mon, Dec 03, 2001 at 01:00:41PM -0500, Sven Heinicke wrote:
 > | 
 > | We have been having many problems on a Dell PowerEdge 4400 with 4G of
 > | memory.  We are willing to get new hardware if, perhaps, there is
 > | something known to not work with that hardwares memory.  If there are
 > | known hardware configurations that work will in high load, high IO
 > | situations.  We really want to stay with Linux, but my boss is getting
 > | increasingly agitated with issues.
 > | 
 > | Our application has, on the order of 300 network sockets open at any
 > | one time primarily for input.  And only 1 or 2 for output.  We
 > | constantly malloc/free 100k of memory, I mean a lot.  Plus do a fair
 > | amount of SCSI IO.  The threads never use more then like 300M of
 > | memory at a time though caching memory fills up to like 2G.  I believe
 > | it would work on a system with 1G of memory.
 > | 
 > | With kernels 2.4.14 and before, including some AA kernels, the cache
 > | would fill up memory and do a little swapping to disk and then start
 > | the just-in-time free memory stuff.  We where very happy when 2.4.16
 > | seems smarter about this then previous version and never uses more
 > | then ~2G of cachememory.
 > | 
 > | But, after running for a time, kswapd starts taking more CPU time then
 > | the threads we are running and slowing down the processing.  Is this
 > | something wrong with kswapd or might modifying files in /proc/sys/vm/
 > | fix this?
 > | 
 > | If modifying files in /proc/sys/vm/ can fix it, what should one
 > | consider when modifying the /proc/sys/vm/kswapd and other files to
 > | suit my applications?  Also, in my /proc/sys/vm directory there is
 > | only the following files:
 > | 
 > | $ ls /proc/sys/vm
 > | bdflush  max-readahead  overcommit_memory  pagetable_cache
 > | kswapd   min-readahead  page-cluster
 > | 
 > | With 2.4.16 I though I should have others as described in the proc.txt
 > | file, like `buffermem', `pagecache' and others.  How do I get these,
 > | and once I do have them some hints on how to modify there values to
 > | optimize my applications might be useful.
 > | 
 > | 	 Sven
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