Hi, Adam,
Many thanks for your suggestion. It works with shrinking KMEM_SIZE from 16MB to 1MB(JDB disabled). By printing kernel memory usage by Kmem_alloc::debug_dump(), it seems only 758KB used in the following message.
"Used 758KB out of 1024KB of Kmem"
Now I can get a larger continuous memory area on my platform. Thanks again.
BRs, Jesse -----Original Message----- From: l4-hackers [mailto:l4-hackers-bounces@os.inf.tu-dresden.de] On Behalf Of Adam Lackorzynski Sent: Monday, December 19, 2016 6:46 AM To: l4-hackers@os.inf.tu-dresden.de Subject: Re: Memory usage analysis and optimization
Hi,
On Fri Dec 16, 2016 at 08:38:28 +0000, Jesse-SC Chou (©P®Ñ¥¿) wrote:
I¡¦m analyzing the memory usage of Fiasco/L4Re/L4Linux. On my platform, there are 128MB physical memory. L4 bootstrap can detect it correctly. ================================================== L4 Bootstrapper Build: #164 Îå 12Ô 9 11:39:51 CST 2016, 4.8.4 Scanning up to 128 MB RAM, starting at offset 32MB Memory size is 128MB (20000000 - 27ffffff) RAM: 0000000020000000 - 0000000027ffffff: 131072kB Total RAM: 128MB ==================================================
The memory regions after boot up and sigma0 loaded:
Regions of list 'regions' [ 20000000, 200001c7] { 1c8} Root mbi_rt [ 20001000, 20001aff] { b00} Kern fiasco [ 20002000, 20092fff] { 91000} Kern fiasco [ 200c0000, 200c9f43] { 9f44} Sigma0 sigma0 [ 200d0000, 200d6177] { 6178} Sigma0 sigma0 [ 20140000, 20168c27] { 28c28} Root moe [ 20170000, 2017b58b] { b58c} Root moe [ 21000000, 2100e5e3] { e5e4} Boot bootstrap [ 21100000, 21a2dfff] { 92e000} Root Module
SIGMA0: Hello! KIP @ 20002000 allocated 4KB for maintenance structures SIGMA0: Dump of all resource maps RAM:------------------------ [4:20000000;20000fff] [0:20093000;200bffff] [0:200ca000;200cffff] [0:200d7000;2013ffff] [4:20140000;20168fff] [0:20169000;2016ffff] [4:20170000;2017bfff] [0:2017c000;210fffff] [4:21100000;21a2dfff] [0:21a2e000;26ffffff] ==================================================
The largest unused continuous memory region are at ¡§0x21a2e000 ~ 0x26ffffff¡¨, which is about 85MB. I would like to make continuous memory region larger and have the following ideas and questions:
Generally: yes, there are tuning possibilities, given that memory and program sizes are known.
The memory used by bootstrap may be freed after the system bring up. If moving ¡§bootstrap¡¨ program to 0x26000000, the ¡§Module¡¨ programs can append to ¡§MOE¡¨ program. The ¡§Module¡¨ will be started ¡§0x207c0000¡¨ (aligned to page size 4KB). Thus, I can get larger continuous memory area that originally separated by ¡§bootstrap¡¨ program. Is this idea correct ?[ 20170000, 2017b58b] { b58c} Root moe [ 21000000, 2100e5e3] { e5e4} Boot bootstrap [ 21100000, 21a2dfff] { 92e000} Root Module
Yes, should generally work I think.
There are a reserved region ¡§0x27000000 ~ 0x27FFFFFF¡¨ not shown in boot log. When I traced into program, this region seems used by sigma0. What is this memory used for? I think 16MB is a very large chunk in current embedded system. Can we compute the amount this area really use and shrink to a smaller size?
That's the memory taken by Fiasco, see src/kern/arm/config-arm.cpp KMEMSIZE. Depending on your use case you can make this smaller.
Adam
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