Re: postgres files in use not staying in linux file cache

[Tim Kane <tim.kane@xxxxxxxxx>]

From: Shaun Thomas <sthomas@xxxxxxxxxxxxxxxx>
Date: Tuesday, 10 June 2014 22:07

So here's the thing. The Linux page reclamation code is *extremely

broken* in everything before 3.11. Take a look at this, then realize

that this is *only one patch* from several that target the memory

manager weightings:

<snipped>

Since you're using Ubuntu 12.04, I strongly suggest upgrading your core

to 12.04.4 and apply the linux-generic-lts-saucy pseudo-package to at

least get onto the 3.11 instead. The 3.2 kernel is pants-on-head

retarded; we've had a lot more luck with 3.8 and above.

Without trying to hijack this thread, is there any documentation around recommended or known-good kernels for Postgres/DB type workloads?

I can see there has been a lot of discussion around recent kernel developments being detrimental (or potentially detrimental) -  http://www.postgresql.org/message-id/20140115141408.GJ4963@xxxxxxx - , but there doesn’t seem to be a definitive resource to know which kernels to avoid.

I ask because I’ve just read your statement above about 3.2 being pants-on-head, and having had more luck with 3.8 and above – despite most installations being on much older (2.6.19) kernels (as per the thread).

I’d be interested to see how much benefit we’d get from moving off 3.2, but I’d like to be aware of the risks of more recent kernel version’s also.

Cheers,

TIm