linux-kernel - Re: mmap dirty limits on 32 bit kernels (Was: [BUG] New Kernel Bugs)

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Message-Id: <200711181513.19559.phillips@phunq.net>
Date:	Sun, 18 Nov 2007 16:13:18 -0700
From:	Daniel Phillips <phillips@...nq.net>
To:	"Rob Mueller" <robm@...tmail.fm>
Cc:	"Linus Torvalds" <torvalds@...ux-foundation.org>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	"Bron Gondwana" <brong@...tmail.fm>,
	"Christian Kujau" <lists@...dbynature.de>,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	"riel" <riel@...hat.com>, "Anton Altaparmakov" <aia21@....ac.uk>
Subject: Re: mmap dirty limits on 32 bit kernels (Was: [BUG] New Kernel Bugs)

On Thursday 15 November 2007 14:24, Rob Mueller wrote:
> > That's my personal opinion, and I realize that some of the
> > commercial vendors may care about their insane customers'
> > satisfaction, but I'm simply not interested in insane users. If
> > they have that much RAM (and bought it a few years ago when a
> > 64-bit CPU wasn't an option), they can't be poor.
>
> From our perspective, the main issue is that some of these machines
> we spent quite a bit of money on the big RAM (for it's day) + lots of
> 15k RPM SCSI drives + multi-year support contracts. They're highly IO
> bound, and barely use 10-20% of their old 2.4Ghz Prestonia Xeon CPUs.
> It's hard to justify junking those machines < 5 years.
>
> We have a couple of 6G machines and some 8G machines using PAE. On
> the whole, they actually have been working really well (hmmm, apart
> from the recent dirty pages issue + reiserfs data=journal leaks +
> inodes in lowmem limits)

Junk everything except the 15K drives, you will be glad you did.  Too 
bad about those multi-year support contracts, hopefully you got a deal 
on them.

Prediction: after these dirty pages issues are gone, there will be more 
dirty page issues because the notion of dirty page limit is 
fundamentally broken.  Your smartest recourse is to re-motherboard to a 
place where the dirty page limit borkage does not hurt as much, and in 
the process you will get a cheap hardware upgrade.  Everybody will be 
happy, the sun will come out, the birds will sing.

Regards,

Daniel
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