Re: [PATCH ] VMSPLIT config options (with default config fixed)

From: Mark Rustad <mrustad@mac.com>
To: Herbert Poetzl <herbert@13thfloor.at>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
	Arjan van de Ven <arjan@infradead.org>, Mark Lord <lkml@rtr.ca>,
	Ulrich Mueller <ulm@kph.uni-mainz.de>,
	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)
Date: Mon, 6 Feb 2006 20:51:01 -0600	[thread overview]
Message-ID: <6D491888-6DEA-4F9B-BEB2-7CD8FDC2159D@mac.com> (raw)
In-Reply-To: <20060207004147.GA21620@MAIL.13thfloor.at>

On Feb 6, 2006, at 6:41 PM, Herbert Poetzl wrote:

> On Mon, Feb 06, 2006 at 03:56:34PM +0100, Jan Engelhardt wrote:
>>>>>> 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.
>>>
>>> it's not really overcommit... it can also be file mmaps or shared  
>>> mmaps
>>> of say tmpfs files (the later is common with oracle actually)
>>
>> So, just as I did in the sample patch, the manual split shall  
>> depend on
>> EMBEDDED. Those who run fat databases with big malloc/mmap  
>> assumptions
>> don't probably belong to the group using CONFIG_EMBEDDED.
>
> *sigh* well, the embeded folks are unlikely to have 1-3GB
> why not use EXPERIMENTAL if you 'think' the option will
> hurt the database folks who do not know to configure their
> kernel ...

Embedded is not the same thing as small. 1GB is what the system I  
work on uses and it is "embedded". This new VMSPLIT is great, BTW.

-- 
Mark Rustad, MRustad@mac.com