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I still don't quite grasp it. He is talking about page outs, but how is disabling the dyn-pager helping with that? Shouldn't page outs only happen when RAM is full?

At my machine with 8 GB RAM and uptime of 4 days I have page outs of only 2 Megabyte. And page ins of 2 Gigabyte.

P.S. I subscribe to your blog! * starstruck




RAM serves (at least) two purposes: holding application data, and caching disk data. Sometimes it can be useful to swap application data out to disk to make more room for disk caching. Imagine if you have an app taking up a whole lot of memory that isn't actively using most of it, and another app reading a lot of data from the disk. In this case, you'll perform better if you swap out all that unused data, and use that RAM to cache disk access for the other app.

What he's saying is happening is that the OS is doing this too aggressively, and that it ends up swapping out data that's actually in use in favor of disk data which doesn't really need to be cached, which hurts performance.

By disabling the pager, you make it impossible to move application data to disk at all. This limits the amount of RAM available for disk caching, but if the OS really is caching too aggressively, that will ensure that it can never page out useful application data by mistake.

My experience mirrors yours, in that it really doesn't seem to be a problem on the computers I've used, but that's what he says he's seeing.

Glad you like the blog, but I'm just a regular guy. I put my pants on with a high speed pants installation robot just like everybody else.




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