General :: Where Does The Kmalloc/Vmalloc/get_free_pages/malloc Allocates Memory
Jul 27, 2011
clarrify the below points:1) Where does the Kmalloc/Vmalloc/get_free_pages/malloc Allocates memory in which space is it Kernel/User?2) Coming to Hardware Point of View is where Kernel/User Space Memory Allocates is it in RAM or any.?3) In Device Drivers, how Open Call get to know whether the hardware is connected/not?
I am new to C and linux. My code below does arbitary writes but I cant figure out where or how it does it.
I am calling the insertNode() function with seq = 'MISSISSPPI$' and alphabets = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ$'
Code:
Weird behaviour I should mention is that when I check for NULL pointer in node->child[index], the unassigned values are not null anymore, they point to arbitary memory.
alloc_task_struct( ) This function allocates 8 KB task_union memory areas. The function takes memoryareas from the cacheif it is at least half-full or if there isn't a free pair of consecutive page frames available.
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.
I'm afraid I have a huge issue with my newest Fedora 14 server. I recently migrated to Fedora 14 from Centos 5, which was very stable, but had ancient packages and libraries and my users were revolting...The machine is a HP ProLiant 360 G7, with 12G RAM and 6 SAS drives in RAID 5.After I migrated to Fedora 14, I noticed that for some reason, during the course of about 24 hours, all usable RAM "disappears" and applications are forced down to swap space. Needless to say I didn't have this issue on CentOS.
The server does heavy IO as per it's function (it's a heavily loaded file processing server and user simulation computing station among other things, which causes lots of random IO), so I thought it may be the cache, but then I realized it cannot be - because obviously Linux will use onyl "unused" RAM for caching and frees it up as soon as an app need it. Then, I thought to check the "slabtop" to see what's going on in Kernel memory. Unfortunately I don't have the screenshot from the time just before the latest crash, but there's a certain value displayed by slabtop, which slowly, byte-from-byte creeps over all available RAM, eventually forcing applications down to the swap. This is malloc-64, and as you can see from the bellow copy-paste, it's building up again even now...
Code: Active / Total Objects (% used) : 9118075 / 9153600 (99.6%) Active / Total Slabs (% used) : 152157 / 152157 (100.0%)
I am developing a code where I need to store the planes of an object in a tree & also i need to store it in a list for further processing ... when I try to allocate using malloc the memory allocation when i checked this in internet , I came to know that it may because the memory that I am trying to allocate may be more than the size_t variable.
When I am trying to run my application on RHEL 6 (Kernel 2.6*), I am getting the following error.*** glib detected *** ./corenms:malloc(); memory corruption : 0x086691d0 ***
First off all, I'm booting from a large MEMDISK using PXE (900MB) . Due to our environment, I cannot decrease the size, nor move files to a nfs/iSCSI/... environment. Everything needs to be in that MEMDISK.
Now, when I try to run the OS, I get out of vmalloc space. How do I increase it to a number which allows such a large image to be mapped? I tried the parameter "vmalloc=1280M", but with that parameter, I don't get past the Booting the kernel screen.
Memory should not be an issue, since the machine(s) have at least 2GB RAM. (900MB MEMDISK + 256MB for other kernel stuff + 768MB for user stuff). The machine(s) have a Pentium 4 Extreme Edition processor, with hyperthreading and SSE2, but no EM64T.
How can I boot the system, and get past that message? Decreasing the MEMDISK size is not possible too. It is at the smallest we can get with our userland + kernel + modules.
I want to edit a grub file, but none of the online instructions exactly match my files. I'm trying to follow the instructions to add vmalloc=256M to a grub file, from here:
I want to use kmalloc() to allocate contiguous memory on ram. But I can not seem to find the required header file(s) like linux/slab.h. I suppose I do not have the required library and I certainly do not know what and where to look.
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?)
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.
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.
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 ?
I am getting a weird compilation error with malloc.h/usr/include/malloc.h:86: error: expected ')' before '__size'This is what the code looks like inside malloc.hextern void *(*__morecore) __MALLOC_PMT ((ptrdiff_t __size))When I did some googling, it was stating that ptrdiff_t was not defined; but, it is.#define __malloc_ptrdiff_t ptrdiff_t
I have been trying to fix this problem for 3 days, any ideas before I jump through the window (not the bill gates one)?I am using ubuntu 9.10 and running a ./configure.
Is there a way to hook calls to new/malloc, delete/free in C++? I tried the following methods: LD_PRELOAD -> fails for malloc, because dlsym seems to depend on malloc -Wl,--wrap,malloc -> doesn't work for 'new' gcc hooks -> doesn't work always, e.g. for uclibc there are no hooks Are there any other methods I could try?
I am looking to buy some memory for my netbook. Currently I have 1 GB of DDR3 memory. However, the specification says that 2 GB of memory is the max. However, when I do the following it says that 4GB is the max:
I am looking for free database that has low memory usage and innodb and memory like engins that has C API and support trigger and client/server support for using in embedded linux systems.