Re: hints at modifying kswapd params in 2.4.16

Sven Heinicke (sven@research.nj.nec.com)
Tue, 4 Dec 2001 13:18:18 -0500 (EST)


hmm, i did some snooping aroudn and I concluded that I worded my
questions wrong (not including bad grammar). My question should be:

What is the latest kernel with the old VM? The 2.4.13-ac8?

Sven Heinicke writes:
>
> 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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