General :: Configure Physical Memory Map?
May 18, 2010
I am trying to build and bring-up Linux (embedded) for a piece of hardware which have MIPS 74K proccessor 16MB Flash, 128MB DDR and network/usb support. How to configure/set into the kernel the exact addresses of the physical memory map? How does the kernel know where is the system ram, i/o memory, root FS? I have read some book and I found how the applications can go and read some special files like /proc/iomem to find out info about memory but what I need is how to set those addresses at the beginning when I build the kernel and FS in order to boot the kernel on my h/w.
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Jan 11, 2010
let me know how to clear cache memory ( RHEL 5.1 ) as it consumes almost 100% physical memory.
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Oct 20, 2010
I am monitoring physical memory in a server I administer, and my hardware provider told me they had increased physical memory size to 4Gb... However, using several tools (free -m; top; dmesg | grep Memory; grep MemTotal /proc/meminfo I discovered that I actually have 3Gb, not 4... But, my doubt comes from the fact that dmesg | grem Memory tells me I have 3103396k/4194304k available The first number is effectively 3Gb, but the second one, is 4! so, why I am looking at this two different numbers?
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Sep 12, 2010
When we want to setup a linux system, there is a common a suggestion like set the swap space as twice as big than your physical memory, I want to know why do we need this and how is this suggestion come from?
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Sep 3, 2010
I am doing a test to get the memory used by apache`s apache2 processes. I used a script to get VmSize and VmRss from /proc/pid/status, and loop through that to get the sum of VmSize and VmRss of all the apache2 processes.
I found the VmSize (about 4GB) and VmRss (about 3.4GB) are much larger than the physical memory (1GB) when apache server was saturated. It was said because of the multi-counted libiraries size used by many processes simultaneously. Then , how to get the physical memory used by apache2 processes? Or how to get a more reasonable memory data?
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Feb 21, 2010
A process is trying one access to memory, for example through an array (ex.: vect[0]=123. What happens?
Here below what I guess but I'm not sure and accept any comment (please, distinguish between "the system" and "the CPU" in case).
Let's suppose swapping to disk disbled.
We have two scenarios: without and with cache.
If no cache is present in the system:
1. The CPU must discover the phys addr of vect[0] virtual addr. To do that, has to read from 3 (or 2 depending on the system?) pages tables, stored in memory as well.
2. The CPU writes to the final address.
These mean 4 memory accesses.
If cache is present:
1. Like above but, if the pages tables are in cache, we have 3 accesses to that.
2. If the req. page is not in cache, it's reads from ram and transferred to it. Afterwards, cache is written.
In the best case we have 4 cache accesses.
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Jun 26, 2010
I have a 32 bit Ubuntu installed and my Laptop has 4GB RAM, but only 3GB is considered by Linux. My question is: what is the reason for the upper limit on physical memory ?
Code:
dmesg | grep Memory [0.000000] Memory: 3052428k/3112960k available (4673k kernel code, 56364k reserved, 2121k data, 656k init, 2200904k highmem) I am familiar with the virtual memory concept where linux splits upper 1GB for kernel and lower 3GB for user processes. In total, linux 32bit can address 4GB virtual addresses. Does this meant that 1GB of physical memory is already mapped to 1GB of kernel space and Linux only shows the remaining 3GB physical memory left for the user in the above command.
I did some searching on the internet and found some articles related to this, but it only confused me further since some articles suggest 4GB is the upper limit with mentioning whether it's virtual or physical memory, some bring in the concept of PAE, etc. I'm relative new to Linux's memory management, so it'd be really helpful if someone could answer this.
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Nov 4, 2010
As i undertsand - out of 1GB of the virtual Address space for Kernel from 3GB to 4GB of the process address space, Kernel image (code, data, bss, stack, heap) resides staring @0x0 address. Vmalloc area starts either at the end of Physical ram size or at 896M. This 896M cap is mandated to ensure that minimum of 128MB is reserved as vmalloc_reserve for vmalloc,kmap etc.
Is the understanding correct? Now trying to map Physical Zones into this 1GB address space
Initial 16MB is mapped to ZONE_DMA
16MB - 896MB is mapped to ZONE_NORMAL
896MB - 1024MB is mapped to ZONE_HIGHMEM
Does this mean that Kernel image is residing in ZONE_DMA area? Any call to vmalloc() in kernel code will return address beyond 896M? insmod of any LKM will internally invoke vmalloc() to obtain contiguous area - where will this code physically located along with rest of kernel code in ZONE_DMA or in ZONE_HIGHMEM?
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Jan 23, 2011
I'd like to ask you how install new physical memory in my hp ml350 g6 server with linux redhat operating system>
i sugess it is easy like in windows operating system but there is frind told me you must make mount , i am new with linux os .
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Apr 13, 2010
How can I get the physical address corresponding to a virtual address in linux by using /proc file system
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Aug 30, 2010
I got the VMrss used by a process as about 2GB, but the physical memory of my computer is only 1G.
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Oct 24, 2010
I have a system with 2G of memory and swap memory of 4G.
This is the output from :
PHP Code:
How could they do to the memory cache to be used as much? Because, occasionally, swap is used and note that the system could use the memory cache does not swap ...
Slackware current 64 multilib.
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Aug 27, 2010
I have rhgel5.3 installed on IBM blade server having 16 GB of physical memory. But it showing only 4GB.
#cat /proc/meminfo
#free -m
#top
[code]...
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Jun 20, 2010
Why linux uses swap space, even if there are free physical memory available.
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Jan 2, 2011
Before running SOSreport, the free physical memory is 5389Mb out of 8Gb.
After running SOSreport, the free physical memory is 3229Mb.
Why is this so? how we can free up the physical memory.
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May 11, 2010
I have a system with 1 GB RAM. I'm running KDE 4. I created a tab to look that the Physical Memory in the System Monitor program, which I assume appears to look at the same stats that "top" looks at. In that Physical Memory tab I have 3 tables: Used Memory, Free Memory, and Application Memory.The Used Memory table shows that the system is using .94 of .98 GiBytes. The Free Memory table shows that the system has .5 GiBytes of RAM free.
However the Application Memory shows that only 339 M-Bytes of RAM is being used.Note that "top" shows the same info.So where is the other .6 GiBytes of RAM that the Used Memory table shows as being used?If I look at the process table which is supposed to encompass all of the processes running, including the ones for the OS, then it appears to add up to the 339 M-Bytes being used in the Application Memory table. Is the rest of the memory being held in reserve by the OS to be used as needed? If so, then why when another application is opened the Free Memory goes down instead of staying constant?I also noticed this memory "black hole" when I was running 11.0 on a system with 4 GB of RAM. The OS appeared to "take up" a large chunk of memory that was NOT being used by any applications and making it "disappear" - meaning that the applications were using about 1.3 GiBytes of RAM and Free Memory was showing only .7 GiBytes instead of the over 2 GB of RAM that should be free.
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Oct 22, 2009
I allocated a chunk of memory using kmalloc in a Device Driver. Kmalloc provides a pointer to the allocated memory. This is one of my first few drivers.
I assume that the address returned is a Virtual address. I need to find the physical address of the memory location. I am working on an Intel 64 bit Fedora machine. I used the virt_to_phys() routine present in <asm/io_64.h>. I found that this routine returns an unsigned long value (32 bit) instead of an unsigned long long value (64 bit). Moreover, it seems that it simply returns the address - OFFSET instead of extracting the value in the page tables.
So is there any function / system call in Linux which will allow me to see the actual physical address on the Intel 64 arch.
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May 2, 2010
Whenever I'm running my application process, I've 1M physical memory usage is increasing for every 2 hours.This I observed using 'free -m' command.But 'top' command did not showing any increase 'RSS' size.It is same as it was started initially.Even though I stopped my process,the increased memory was not released back. If I start my application process then again memory usage start increasing by 1M for every 2 hours. increase of memory usage observer with 'free' and that too when my application is running, but top command is not showing any change in the RSS sizeIf my application is leaking any memory which is allocated by new/malloc, that should be released back whenever my application exit and the size increase will be show through top command for that process, right? This is not happeningThis proves that there is no potential leaks in my process.But why physical memory is increasing when only my process is running?
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Dec 17, 2008
When I try to access at physical address (0xD0000), we known that it is necessary to convert physical address to virtual address using function IOREMAP(0xD0000, 1024) and return me 0xC00D0000.
Now our doubt is when I have a board with I/O in address 0x150, is it necessary to convert this address to other virtual address??? or with inb(0x150) return me state of I/O in this address? How can I known where is this I/O address in my map memory?
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Jan 1, 2011
i need some information about how Debian 5 manage the physical memory . such as the memory management algorithms. i have googled it a lot but i couldn't find it.
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Jul 24, 2010
I have a home server set up with samba, proftp, and the torrentflux webUI via apache and mysql. To the best of my ability, I have stripped the system of any unnecessary software. After a fresh reboot the system uses around 250 mb of memory, which to me still seems like a lot, and after it has been on for a few hours with torrents downloading, the memory usage will steadily climb to and stay at 2 gb! Using top shows that the processes using the most memory are python, mysqld, and apache2. What the heck is going on?
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Aug 20, 2010
First of all I'm not a very experienced linux user, I have installed fedora 13 on my HP Laptop and it has 8Gb installed, (confirmed in Bios) grep MemTotal /proc/meminfo
MemTotal: 3088492 kB It's less then 8Gb
googling about it it seems that I ineed PEA support for my kernel. It seems that fedora 13 should install this if needed, correct me if I'm wrong. uname -a Linux mjohanss-pc.kentor.se 2.6.33.6-147.2.4.fc13.i686 #1 SMP Fri Jul 23 17:27:40 UTC 2010 i686 i686 i386 GNU/Linux If PEA support was installed I think PEA should be seen after .fc13.i686 in the output. How can I install and configure PEA support so all my memory is recognized?
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Aug 17, 2010
configure IfModule mpm_worker_module and mpm_prefork_module by memory Example : I have 1 server ubuntu linux use Apache+PHP - How to configure :
[Code]...
for : 1Gb or 2 Gb - Have math configure <IfModule mpm_worker_module> </IfModule> by memmory?
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Apr 20, 2010
I am using malloc and frees a lot in my program. It shows its allocated but when i remove it doesnt show as the memory is removed(I am using the top command to view VIRT memory usage). If this continously grows what would happen to my program (Will it go out of memory?)
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Mar 18, 2011
I have a computer with 16GB of ram. At the moment, top shows all the RAM is taken, (NOT by cache), but the RAM used by the various processes is very far from 16GB.I have seen this problem several times, but I don't understand what is happening.My only remedy so far has been to reboot the machine.
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Aug 22, 2010
This is my first post in these forums. I'm still quite new to Linux (using Mint 9) so please bear with my not-very-articulate question(s)When I boot up and open up a tty terminal I get a message saying "Memory corruption detected in low memory." I've done an extensive google search about the issue and it seems not uncommon. I ran a memtest with no errors returned, so I'm sure that there's nothing really wrong with the memory; apparently it's a bug in the kernel that's causing this.
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Jan 17, 2010
I found from command 'top' that 8GB memory are used. However, using command 'ps' with some options to grep the running processes and then summing up the memory used by the running processes are less than 2 GB. Where has the used memory gone ?
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Feb 5, 2011
I understand the software RAID partition types on two physical drives that will be paired must be set to the same size. However,
1. Do the physical drives themselves need to be the same size?
2. Do the physical drives need to use the same interface?
e.g. Can I setup mirroring with one 80G SATA, and one 320G PATA? (And is this reliable/stable?). The use is for an asterisk server which came with the 80G, I can't find anything smaller than 320G for the 2nd drive, and the free connector inside is PATA.
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Oct 4, 2010
Is it possible if I am only using ext3 and no LVM or anything else to re-size the partition into another physical device? I am pretty sure the answer to this is no but I was still curious as I am facing a full 1tb disk and need to add a new drive and unsure how to do this due to shared folders existing on the old drive and no way to actually expand them without linking in new files or something.
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Jun 30, 2011
We are working on our subscription renewal and now since Red Hat has changed their subscription model we need to give them the number of physical CPU sockets on each system.I have tried looking thru /proc/cpuinfo as well as tried to parse data out from dmidecode but both of those solutions count each individual core as a CPU.Is there a clean and easy way to determine the number of sockets on each system? We also use RHN Satellite to manage our systems but I believe that is pulling the same data from dmidecode
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