Re: Checkpoint distribution

On Mon, Apr 14, 2014 at 9:42 AM, Borodin Vladimir <root(at)simply(dot)name> wrote:

> 14 апр. 2014 г., в 19:11, Jeff Janes <jeff(dot)janes(at)gmail(dot)com> написал(а):
>
>
> During the writing phase of the checkpoint, PostgreSQL passes the dirty
> data to the OS. At the end, it then tells the OS to make sure that that
> data has actually reached disk. If your OS stored up too much dirty data
> in memory then it kind of freaks out once it is notified it needs to
> actually write that data to disk. The best solution for this may be to
> lower dirty_background_bytes or dirty_background_ratio so the OS doesn't
> store up so much trouble for itself.
>
>
> Actually, I have already tuned them to different values. Test results
> above have been obtained with such settings for page cache:
>
> vm.dirty_background_ratio = 5
>

If you have 64GB of RAM, that is 3.2GB of allowed dirty data, which is
probably too much. But I think I've heard rumors that the kernel ignores
settings below 5, so probably switch to dirty_background_bytes.

Cheers,

Jeff