Re: dirty_ratio & dirty_background_ratio settings with huge memory

On 03/06/2018 01:16 PM, Laurenz Albe wrote:
> pinker wrote:
>> I've got cutomer with really huge RAM, now it's:
>>              total       used       free     shared    buffers     cached
>> Mem:       3102111    3052596      49515     208801        992    2961185
>> -/+ buffers/cache:      90418    3011693
>> Swap:         8191          1       8190
>>
>> (free -m)
>>
>> and before it was twice more (6TB).
>>
>> and trying to figure out how to set dirty_ratio & dirty_background_ratio
>> parameters. Even for normal sized server those default sizes are to high,
>> but now would be ridiculously huge, respectively 1,24TB and 300GB. 
>> I'm thinking about 1 percent for dirty_ratio and not using
>> dirty_background_ratio because it's not possible to set it below 1% but to
>> set dirty_background_bytes instead to about 1-2GB.
>> Maybe someone has got other experience with RAM of this size and those
>> settings?
> 
> Yes, you should set vm.dirty_background_bytes and vm.dirty_bytes
> and not use the *_ratio settings.
> 
> 2 GB for vm.dirty_background_bytes and 1 GB for vm.dirty_bytes sounds fine.
> 

It should be the other way around: dirty_background_bytes < dirty_bytes

regards
-- 
Tomas Vondra                  http://www.2ndQuadrant.com
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