Date: Tue, 9 Mar 2004 20:57:52 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Andrea Arcangeli <andrea@suse.de>
Cc: Arjan van de Ven <arjanv@redhat.com>, Linus Torvalds <torvalds@osdl.org>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: objrmap-core-1 (rmap removal for file mappings to avoid 4:4 in <=16G machines)
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* Andrea Arcangeli <andrea@suse.de> wrote:

> > (OASB is not a full-disclosure benchmark so i have no way to check
> > this.) All you have proven is that workloads with a limited number of
> > per-inode vmas can perform well. Which completely ignores my point.
> 
> what is your point, that OASB is a worthless workload and the only
> thing that matters is TPC-C? [...]

not at all. I pointed out specific workloads that create tons of vmas,
which would perform very bad if swapping. OASB is not one of those
workloads. [I could also mention UML which currently creates a vma per
virtualized page, which, with a low-end UML setup, generates tens of
thousands of vmas as well.]

(if the linear search is fixed then i have no objections, but for the
current code to hit any mainline kernel we would first need to redefine
'enterprise quality'. My main worry is that we are now at a dozen emails
regarding this topic and you still dont seem to be aware of the severity
of this quality of implementation problem.)

sure, remap_file_pages() fixes such problems - while i'm happy if more
people use remap_file_pages(), apps are not (and should not be) forced
to use remap_file_pages() and i refuse to concede that the VM must
inevitably get wedged with just a couple of thousand vmas created on a
256 MB 500 MHz box ... I dont know how to put this point in a simpler
way. This stuff must not be added (to mainline) until it can take the
load.

	Ingo
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