Re: Scalability in postgres

On 5/28/09 6:54 PM, "Greg Smith" <gsmith(at)gregsmith(dot)com> wrote:

> 2) You have very new hardware and a very old kernel. Once you've done the
> above, if you're still not happy with performance, at that point you
> should consider using a newer one. It's fairly simple to build a Linux
> kernel using the same basic kernel parameters as the stock RedHat one.
> 2.6.28 is six months old now, is up to 2.6.28.10, and has gotten a lot
> more testing than most kernels due to it being the Ubuntu 9.04 default.
> I'd suggest you try out that version.

Comparing RedHat's 2.6.18, heavily patched, fix backported kernel to the
original 2.6.18 is really hard. Yes, much of it is old, but a lot of stuff
has been backported.
I have no idea if things related to this case have been backported. Virtual
memory management is complex and only bug fixes would likely go in however.
But RedHat 5.3 for example put all the new features for Intel's latest
processor in the release (which may not even be in 2.6.28!).

There are operations/IT people won't touch Ubuntu etc with a ten foot pole
yet for production. That may be irrational, but such paranoia exists. The
latest postgres release is generally a hell of a lot safer than the latest
linux kernel, and people get paranoid about their DB.

If you told someone who has to wake up at 3AM by page if the system has an
error that "oh, we patched our own kenrel build into the RedHat OS" they
might not be ok with that.

Its a good test to see if this problem is fixed in the kernel. I've seen
CentOS 5.2 go completely nuts with system CPU time and context switches with
kswapd many times before. I haven't put the system under the same stress
with 5.3 yet however.