[Lustre-discuss] Lustre 2.0 client cache size

[Jay]

After checking 2.6.35 kernel source code, POSIX_FADV_NOREUSE actually doesn't do anything. So I don't know how it helps. Probably we should do POSIX_FADV_DONTNEED after reading?

Jay

On Mar 17, 2011, at 5:43 PM, Oleg Drokin wrote:

> Hello!
> 
> On Mar 17, 2011, at 5:44 PM, Andreas Dilger wrote:
>>> I did not find if this was removed or this was partially included in 
>>> Lustre 2.0.
>>> What's the current status of this and how can I tell to my client to 
>>> avoid caching too many data?
>> The client VM usage was one of the areas that was completely rewritten by Nikita for 2.0, so it was likely this functionality was lost at that time.  I don't have any idea at this time how hard it would be to restore.
> 
> I wonder if the generic vm tunables could be used instead? I think that was the original plan.
> 
>>> Those clients do a lot of read and write in Lustre filesystems but 
>>> thoses files will not be re-read soon, so it is useless to fill memory 
>>> with it. Moreover, when the client memory is full, Lustre performance 
>>> are really impacted.
>> It may be possible to use fadvise(FADV_NOREUSE) from the application to cause the VM to discard these pages after the first use.
> 
> Yes, that would totally make sense to do regardless of other methods.
> 
> Bye,
>    Oleg
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