Re: Reducing inode cache usage on 2.4?

[James Pearson]

Andrea Arcangeli wrote:
> My only suggestion for 2.4 is to try with vm_cache_scan_ratio = 20 or
> higher (or alternatively vm_mapped_ratio = 50 or = 20).  There's a
> reason why everything is tunable by sysctl.
>
> I don't think the vm_lru_balance_ratio is the one he's interested
> about. vm_lru_balance_ratio controls how much work is being done at
> every dcache/icache shrinking.
>
> His real objective is to invoke the dcache/icache shrinking more
> frequently, how much work is being done at each pass is a secondary
> issue. If we don't invoke it, nothing will be shrunk, no matter what is
> the value of vm_lru_balance_ratio.
>
> Hope this helps funding an optimal tuning for the workload.

Setting vm_mapped_ratio to 20 seems to give a 'better' memory usage 
using my very contrived test - running a find will result in about 900Mb 
of dcache/icache, but then running a cat to /dev/null will shrink the 
dcache/icache down to between 100-300Mb - running the find and cat at 
the same time results in about the same dcache/icache usage.

I'll give this a go on the production NFS server and I'll see if it 
improves things.

Thanks

James Pearson




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