Re: kernel version impact on PostgreSQL performance

On Tue, Mar 09, 2010 at 11:58:58AM -0500, Greg Smith wrote:
> Rodger Donaldson wrote:
> >Cyril Scetbon wrote:
> >>Does anyone know what can be the differences between linux kernels
> >>2.6.29 and 2.6.30 that can cause this big difference (TPS x 7 !)
> >>http://www.phoronix.com/scan.php?page=article&item=linux_2624_2633&num=2
> >
> >http://www.csamuel.org/2009/04/11/default-ext3-mode-changing-in-2630
>
> Yeah, I realized I answered the wrong question--Cyril wanted to know
> "why was 2.6.30 so much faster?", not "why did 2.6.33 get so much
> slower?", which is what I was focusing on. There's a good intro to what
> happened to speed up 2.6.30 at http://lwn.net/Articles/328363/ , with
> the short version being "the kernel stopped caring about data integrity
> at all in 2.6.30 by switching to writeback as its default".
>
> The give you an idea how wacky this is, less than a year ago Linus
> himself was ranting about how terrible that specific implementation
> was: http://lkml.org/lkml/2009/3/24/415
> http://lkml.org/lkml/2009/3/24/460 and making it the default exposes a
> regression to bad behavior to everyone who upgrades to a newer kernel.

The whole O_PONIES debacle, while possibly gratifying to a small
number of kernel developers, left a pretty foul taste in my mouth, and
th deliberate knobbling of ext3 so it wouldn't be more reliable than
ext4 was... words fail me, really. I don't know what Linux was
thinking when he accepted that patch. I'm glad the distributors
pretty much all announced they'd over-ride that behaviour in any
kernels they ship.

Suffice to say none of that mess inspired much confidence in ext4 for
me.

--
Rodger Donaldson rodgerd(at)diaspora(dot)gen(dot)nz
After what Turing did to help win the war, the British government should have
provided him with his own unit of lithe and willing young sailors.
-- pjdoland