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Date: Sun, 5 Feb 2006 22:14:00 +0100 (MET)
From: Jan Engelhardt <jengelh@linux01.gwdg.de>
To: Arjan van de Ven <arjan@infradead.org>
cc: Mark Lord <lkml@rtr.ca>, Ulrich Mueller <ulm@kph.uni-mainz.de>,
       Herbert Poetzl <herbert@13thfloor.at>, linux-kernel@vger.kernel.org,
       Jens Axboe <axboe@suse.de>, Linus Torvalds <torvalds@osdl.org>,
       Byron Stanoszek <gandalf@winds.org>, Ingo Molnar <mingo@elte.hu>,
       Andrew Morton <akpm@osdl.org>
Subject: Re: [PATCH ]  VMSPLIT config options (with default config fixed)
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>> >
>> > Mmm.. bad idea.  As much as I'd like the default to be 3GB_OPT, that would
>> > be a big impact to userspace, and there's no point in breaking everyone's
>> > machines when advanced users can just reconfig/recompile to get what they want.
>> >
>> What userspace programs do depend on it?
>
>there is a lot of userspace that assumes they can do 2Gb or even close
>to 3Gb of memory allocations. Databases, java, basically anything with
>threads. Sure for most of these its a configuration option to reduce
>this, but that still doesn't mean it's a good idea to change from the
>existing behavior...
> 
Not to mention that these (almost(*)) fail anyway when you have less than 2 
GB of RAM.

(*) when finally writing to overcommitted memory

Yuck. That sounds like they depend on 64G/64bit allocations on 4G/32bit 
machines.


Jan Engelhardt
--