linux-kernel - Re: [PATCH] x86_32: trim memory by updating e820 v2

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Message-ID: <20080128150957.GA12205@elte.hu>
Date:	Mon, 28 Jan 2008 16:09:57 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Justin Piszcz <jpiszcz@...idpixels.com>
Cc:	Yinghai Lu <Yinghai.Lu@....COM>,
	Jesse Barnes <jesse.barnes@...el.com>, Andi Kleen <ak@...e.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] x86_32: trim memory by updating e820 v2


* Justin Piszcz <jpiszcz@...idpixels.com> wrote:

> Tried it, it worked successfully!
>
> With stock kernel, previous way I had to use it was mem=8832M and top 
> showed this:
>
> top - 18:53:52 up 1 min,  2 users,  load average: 1.03, 0.30, 0.10
> Tasks: 169 total,   1 running, 168 sleeping,   0 stopped,   0 zombie
> Cpu(s):  6.1%us,  2.6%sy,  4.5%ni, 81.3%id,  5.5%wa,  0.0%hi,  0.0%si,  0.0%st
> Mem:   8039464k total,  1288948k used,  6750516k free,     3640k buffers
> Swap: 16787768k total,        0k used, 16787768k free,   178528k cached
>
> With kernel you mentioned and use e820 v3:
>
> top - 18:48:13 up 3 min,  6 users,  load average: 1.67, 0.68, 0.25
> Tasks: 195 total,   2 running, 193 sleeping,   0 stopped,   0 zombie
> Cpu(s): 18.5%us,  1.2%sy,  1.6%ni, 74.8%id,  3.9%wa,  0.0%hi,  0.0%si,  0.0%st
> Mem:   8037668k total,  1438732k used,  6598936k free,     6844k buffers
> Swap: 16787768k total,        0k used, 16787768k free,   273928k cached
>
> No append mem= required.
>
> A full dmesg is attached so you can analyze the e820/MTRR mapping.

thanks for testing it! The code indeed successfully trimmed your memory 
map by 64MB:

from:

 [    0.000000]  BIOS-e820: 0000000100000000 - 000000022c000000 (usable)

to:

 [    0.000000]   modified: 0000000100000000 - 0000000228000000 (usable)
 [    0.000000]   modified: 0000000228000000 - 000000022c000000 (reserved)

what happened on your box previously when you booted without any 
trimming - did it sometimes slow down or something like that?

	Ingo
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