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Questions tagged [memory-management]

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0
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1answer
21 views

Does the kernel address region in user page tables need to be updated in an 64 bit system?

In 32 bit systems with more than 896 MB of RAM it is obvious, that the mapping of kernel addresses need to be changed because of kernel virtual addresses and the non-continuous mapping. But how is ...
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0answers
34 views

How to force the kernel to always maintain at least some page cache?

Is there any way to force the kernel to always maintain at least some page cache for writeback caching purposes, even when faced with memory pressure? I have a rather special use case, where swapping ...
0
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1answer
55 views

How to Increase RAM usage without increasing Cache.?

Amount of memory utilized in RAM is getting stored in Cache . Is there any way to manually increase RAM usage without increasing cache. Below the sample where increasing RAM is also increasing cache. ...
2
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2answers
225 views

What is Address Binding?

I have found some explanations about what "address binding" is. They say that "address binding is an operation of mapping virtual or logical addresses to physical addresses." Is this definition ...
11
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2answers
369 views

What's the lifespan of a file descriptor?

As described here, redirections use open() to write to a file. There's an inner (?) file descriptor created in the shell, and then used when needed. Is the inner descriptor created for the whole ...
0
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3answers
117 views

What happens if a Linux distro is installed with no swap and when it’s almost out of RAM executes a new application? [duplicate]

What happens if a Linux, let’s say Arch Linux or Debian, is installed with no swap partition or swap file. Then, when running the OS while almost out of RAM, the user opens a new application. ...
2
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0answers
49 views

How to check whether physical page is in-use?

I am implementing kernel thread which scans whole physical pages in memory and inspect physical page frame numbers of in-used pages. At first, I thought I can check whether specific page is used by ...
1
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1answer
1k views

Kernel address space and Kernel page table

I am studying Professional Linux Kernel Architecture and I am in Chapter 3 Memory Management. While I studied kernel address space itself is split into direct mapping area, vmalloc area, kmap area and ...
2
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1answer
70 views

How does Qubes do memory management, especially with regard to shared objects?

I'm just reading about Qubes OS, and I have a very simple question -- how does it do memory management and shared object use? Feel free to correct any misconceptions or errs in vocab, but we have the ...
8
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2answers
713 views

Why read-only memory mapped regions have dirty pages?

Executing (for example) the following command to get the list of memory mapped pages: pmap -x `pidof bash` I got this output: Why some read-only pages are marked as "dirty", i.e. written that ...
3
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1answer
899 views

How does the kernel address swapped memory pages on swap partition\file?

A swap partition doesn't contain a structured filesystem. The kernel doesn't need that because it stored memory pages on the partition that's marked as swap area. Since there could be several memory ...
3
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0answers
45 views

How to handle exceptional page when allocating contiguous cache pages in Linux

I have a kernel module code which allocates contiguous cache pages. I use radix_tree_for_each_contig(). Here is the partial snippet of the code. radix_tree_for_each_contig(slot, tree_root, iter, ...
7
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1answer
112 views

How is the page cache mapped in the kernel on 64-bit x86 architectures?

On a modern 64-bit x86 Linux, how is the mapping between virtual and physical pages set up, kernel side? On the user side, you can mmap in pages from the page cache, and this will map 4K pages in ...
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0answers
25 views

is there difference between running an application from nand and ramdisk?

I'm using an application on an embedded linux platform. I copied this application to a nand device with a jffs2 filesystem and ran it from there and system performance is significantly degraded. I ...
1
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1answer
60 views

Determing if an embedded Linux system runs uClinux

I have an ARM Linux system running kernel version 2.4, but I'm not sure if the processor has a memory-management unit, so how can I tell whether the system is running a uClinux kernel or a vanilla ...
0
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1answer
586 views

Redhat: Swap Memory Used is Much Higher Than Total

The top command showed the following information: Mem: 132110132k total, 10447536k used, 121662596k free, 76120k buffers Swap: 16777212k total, 18446744063504593392k used, 10221735436k free, ...
3
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1answer
669 views

Creation of the heap region/segment in Linux

It's my understanding that on Linux the process loader doesn't automatically create a "heap" region for a process like it's the case for the stack, is that correct? I used /proc/$$/maps and before ...
1
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1answer
587 views

Why does my process take too long to die?

Basically I'm using Linux 2.6.34 on PowerPC (Freescale e500mc). I have a process (a kind of Virtual Machine that was developed in-house) that uses about 2.25 G of mlocked VM. When I kill it, I notice ...
2
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1answer
669 views

How does the kernel decides what pages commit to swap?

If RAM usage is higher than the level written in «swapiness», kernel will use SWAP. Ok. But how does the kernel «order» programs? Is it «first come, first served» for RAM? Or biggest programs in ...
0
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1answer
80 views

managing resources on a debian server

We have a debian server shared by all group members to run their memory/cpu (64GB RAM and 23 cores) intensive codes on it. The problem is sometime one code overload the whole server and no one else ...
1
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0answers
250 views

GFP mask of 0x200da on a 64-bit system?

Recently, an OOM showed a GFP mask of 0x200da on a 64-bit system. How is that possible? 0xa would suggest we are talking about Movable Highmem, see: http://lxr.free-electrons.com/source/include/linux/...
1
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1answer
582 views

USB flash drive file transfers seem to hang multiple times during file transfer

I've got Scientific Linux 6.4 Installed (RHEL6.4) and am having trouble transferring to and from USB flash drives... Transfer seems to hang multiple times during transfer to the device, and transfer ...
11
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1answer
6k views

Zswap, Zram, Zcache desktop usage scenarios

I've been trying to understand the difference in use cases for Zswap, Zram, and Zcache. Apologies in advance for the long/slightly sloppily worded question. I've done a bunch of googling, and I ...
15
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2answers
122k views

How to clear memory cache in Linux [duplicate]

Is there any command that by using I can clean the cache in RHEL? I used this command: sync; echo 3 > /proc/sys/vm/drop_caches but it didn't work.