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Re: [BULK] Problems with vacuum!

From: "Scott Marlowe" <smarlowe(at)qwest(dot)net>
To: "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>
Cc: "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Domenico Sgarbossa" <domenico(at)xtecnica(dot)com>,pgsql-performance(at)postgresql(dot)org
Subject: Re: [BULK] Problems with vacuum!
Date: 2004-06-18 18:58:27
Message-ID: 1087585107.28062.16.camel@localhost.localdomain (view raw, whole thread or download thread mbox)
Lists: pgsql-performance
I believe it was more like the kernel was tuned to make it less common,
but certain things can still trigger it.  I know the problem was still
there in the 2.4.24 on the last server I was playing with, but it was a
lot less of a problem than it had been under 2.4.9 on an earlier machine
with the same basic amount of memory.

On Fri, 2004-06-18 at 12:47, Joshua D. Drake wrote:
> Hello,
> I would have to double check BUT I believe this is fixed in later 2.4.x 
> kernels as well. If you don't want to go through the hassle of 2.6 
> (although it really is a nice kernel) then upgrade to 2.4.26.
> Sincerely,
> Joshau D. Drake
> Scott Marlowe wrote:
> > On Fri, 2004-06-18 at 09:11, Tom Lane wrote:
> > 
> >>"Domenico Sgarbossa" <domenico(at)xtecnica(dot)com> writes:
> >>
> >>>so when the users go home, i've got something like 15/20000kb free ram, the
> >>>rest is cached and 0kb of swap...
> >>>It seems that when pg_dump starts the cached memory isn't released so the
> >>>system begin to swap,
> >>
> >>A sane kernel should drop disk buffers rather than swapping.  We heard
> >>recently about a bug in some versions of the Linux kernel that cause it
> >>to prefer swapping to discarding disk cache, though.  It sounds like
> >>that's what you're hitting.  Look into newer kernels ...
> > 
> > 
> > This was a common problem in the linux 2.4 series kernels, but has
> > supposedly been fixed in the 2.6 kernels.  Having lots of memory and
> > turning off swap will "fix" the problem in 2.4, but if you run out of
> > real mem, you're hosed.
> > 
> > 
> > ---------------------------(end of broadcast)---------------------------
> > TIP 4: Don't 'kill -9' the postmaster

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