pinker wrote: > Laurenz Albe wrote > > 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. To repeat (for the archive): it should be the other way round. > Thank you Laurenz. I was always wondering why not to set bigger window > between those 2. Because setting dirty_background_bytes seems quite natural > for me, i.e. start to write asynchronously faster, but why to provoke stalls > faster? is it not better to stretch the window much wider, like 1GB for > dirty_background_bytes and for instance 20 GB dirty_bytes? it's the Approach > 3: Both Ways from > https://lonesysadmin.net/2013/12/22/better-linux-disk-caching-performance-vm-dirty_ratio/ I'd say that setting vm.dirty_background_bytes low and vm.dirty_bytes very high is not a good idea, at least for databases: - If flushing data to disk in the background can keep up with the write activity, you're fine. But then you'd also be fine with a lower setting for vm.dirty_bytes, right? - If flushing to disk cannot keep up with the write activity, you'll get an I/O spike when everything is flushed to disk at checkpoint time and the database may become unresponsive for a while. The idea behind a low vm.dirty_bytes setting is to avoid one big I/O spike and have several smaller ones instead. Yours, Laurenz Albe -- Cybertec | https://www.cybertec-postgresql.com
