Page outs

[mreg376]

So this is really just my curiosity. I have a 2017 i7 iMac with 64GB of RAM and 1TB SSD. Current uptime is about 17 days. Istat reports that there have been about 134,000,000 page ins (fully understandable of course) but also about 2,500 page outs. I haven't used anything very demanding in the last couple of weeks. So my question is, why would there be page ANY outs with 64GB of RAM? Thanks.

 

[kschendel]

It would depend on exactly what's included in "page outs". Does it include file pages mmap'ed in, modified, and unmapped? Is it only anonymous pages written out due to memory shortage? really hard to answer without knowing what is included and what isn't.

 

[chabig]

So my question is, why would there be page ANY outs with 64GB of RAM?

It’s system logic, it’s automatic, and it’s too complicated for anyone but a system software to fully understand.

 

[wardie]

I don’t think it relates purely to OS level memory management as I believe (I’m not an expert) that also applications can force this via memory mapping files in and then writing out, and this is in the stats if it is happening.