From mboxrd@z Thu Jan  1 00:00:00 1970
From: Dirk Behme <dirk.behme@gmail.com>
Subject: Boot time: Initial main memory initialization optimizations?
Date: Mon, 05 May 2014 17:40:56 +0200
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To: Linux Embedded <linux-embedded@vger.kernel.org>

Hi,

regarding boot time optimization, on an embedded ARM Cortex-A9 based 
system with 512MB or 1GB main memory, we found that initializing this 
main memory takes a somehow large amount of time.

Initializing 512MB takes <= ~100ms, the additional 512MB on the 1GB 
take <= ~100ms additionally, too. So in sum <= ~200ms for 1GB.

Having a short look to this, it looks like most of the time is spent 
in arch/arm/mm/init.c in 
bootmem_init()/arm_bootmem_init()/arm_bootmem_free().

Has anybody already looked into this if there are any optimizations 
possible? Maybe even some hacks, if the main memory size (512MB/1GB) 
is always known? Any pointers?

I'm looking for reducing (a) the overall init time and maybe (b) the 
dependency on the memory size.

Thanks

Dirk