[Lustre-discuss] Lustre 2.0 client cache size

[DEGREMONT Aurelien]

Oleg Drokin a écrit :
> Hello!
>
> On Mar 17, 2011, at 5:44 PM, Andreas Dilger wrote:
>   
>> 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.
>   
So the issue is that 'max_cached_mb' tunable should be removed if it 
makes no sense.

The default with the generic tunable is that you could really control 
how they behave per filesystem.

>>> 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.
>   

Hmm... I do not want to patch 'cp' or 'dd' :)


Aurélien