Re: swapping and the value of /proc/sys/vm/swappiness

[Ray Bryant]

Martin J. Bligh wrote:
> > It seems to me that the 5% number in there is more or less arbitrary. 
> > If we are on a big memory Altix (4 TB), 5% of memory would be 200 GB. 
> > That is a lot of page cache.
>
>
> For HPC, maybe. For a fileserver, it might be far too little. That's the
> trouble ... it's all dependant on the workload. Personally, I'd prefer
> to get rid of manual tweakables (which are a pain in the ass in the field
> anyway), and try to have the kernel react to what the customer is doing.
> I guess we can leave them there for overrides, but a self-tunable default
> would be most desirable.

I agree that tunables are a pain in the butt, but a quick fix would to be at 
least to add that 5% to the set of stuff settable in /proc/sys/vm.  Most
workloads/systems won't need to change it.  Very large Altix systems could 
change it if needed.

I don't think that is at the root of the swappiness problems with 
2.6.9-rc1-mm3, though.

> For instance, would be nice if we started doing writeback to the spindles
> that weren't busy much earlier than if the disks were thrashing.
>
> M.

--
Best Regards,
Ray
-----------------------------------------------
                  Ray Bryant
512-453-9679 (work)         512-507-7807 (cell)
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The box said: "Requires Windows 98 or better",
           so I installed Linux.
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