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Questions tagged [memory]

In computing, memory refers to the state information of a computing system, as it is kept active in some physical structure.

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How to know the profile of a Linux memory dump with Volatility?

I have a Linux memory dump which I need to analyze in order to discover a suspicious PID, however I don't have a profile or anything outside the dump file and using volatility imageinfo doesn't work. ...
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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 ...
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In /proc/meminfo, does Dirty include or exclude Writeback?

Dirty %lu - Memory which is waiting to get written back to the disk. Writeback %lu - Memory which is actively being written back to the disk. -- man proc Does Dirty include Writeback? Or ...
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Loop Device eat up RAM [duplicate]

EDIT: Given link of another thread suggest that newer kernel do not have this issue but I am using latest kernel i.e. 4.18.5. Hence, this issue is either new or newer kernel have this bug In my setup,...
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RAM usage extremely high even without anything running?

Today, I woke my PC up from suspend and it was very slow. I suspected a high RAM usage, then free gave me: renan@vector:~> free -tm total used free shared buff/...
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1answer
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How do I identify all of the configured memory limits for a service started using systemd?

I am chasing an error trying to apply a new tune to postgres. The exact error is: 2018-11-07 22:14:49 EST [7099]: [1-1] FATAL: could not map anonymous shared memory: Cannot allocate memory 2018-11-...
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1answer
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Top showing virtual memory usage of hundreds of gigabytes

On a new virtual machine, top shows that a process of mine consumes 100 GB of virtual memory. I've read that it's possible because of overcommit, however, it's a bit too much. I've never seen anything ...
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40 views

Why is the Linux OOM killer terminating my programs?

I am running a complex workflow via bash scripts, which are using external programs/command to do different things. It runs fine for several hours, but then suddenly the OOM killer terminates programs ...
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1answer
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Htop - using more VIRT memory than I have storage?

I see this mostly with jack-server but I'm also seeing huge virtual memory usage from other processes. Currently, it's evolution building a database (has been for hours now but that's another problem)....
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1answer
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How shall I understand the output of free?

I have read What do the "buff/cache" and "avail mem" fields in top mean? and https://askubuntu.com/questions/770108/what-do-the-changes-in-free-output-from-14-04-to-16-04-mean. ...
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How does Linux make sure to reclaim useless “buffers”, from caching the ext4 journal writes, before anything else (e.g. before swapping at all)

My laptop tends to run with about 256MB counted as "Buffers" - in /proc/meminfo and free -w -h - out of about 8GB of RAM. I'm interested in memory usage. I sometimes get into trouble using too much. ...
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Where else could memory be used other than process, cache and tmpfs?

We have a server that runs a huge server process to cache some data, sometimes the process crashes, and the memory is not freed unless the machine is rebooted. Before the crash if I sum the RSS ...
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1answer
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Memory usage shown with `free` command does not match the utilization from System Monitor

When I am using free -m to check memory status, I get the following: $ free -m total used free shared buff/cache available Mem: 7641 5125 188 739 ...
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1answer
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What is cpu_entry_area?

The documentation of the Linux kernel describes the virtual memory map. It says: fffffe0000000000 - fffffe7fffffffff (=39 bits) cpu_entry_area mapping What is this "cpu entry area"? Is it ...
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Find number of dirty pages (modified pages) for a process

I am trying to track the rate at which pages are being modified by a process in Linux and I came across this Soft Dirty PTEs which certainly can help me. I was also able to find a c script that ...
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1answer
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Where's the page cache store? [closed]

When I learn how the read file work , I know kernel first copy disk data to page cache , then copy from page cache to user space . I don't understand where's the page cache store ? Is it a mapping ...
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1answer
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How can I tell if a memory leak is in user space or kernel space?

I have a large multi-threaded open source application which uses proprietary OpenGL libraries, Wayland Weston, and a proprietary graphics driver in the Linux kernel. The drivers are currently under ...
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1answer
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What is the relation between a line in cpu cache and a page in main memory (and block in disk)?

Computer Systems: A Programmer's Perspective (2nd Edition) [Randal E. Bryant, David R. O'Hallaron] says A block is a fixed-sized packet of information that moves back and forth between a cache and ...
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When do we jump into kernel part of our process virtual memory other than when we use system calls? (In Linux)

This is a follow up question from my previous question. Based on the answer, a system call is an example of when we jump into kernel part of virtual memory of our process. What are other examples ...
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1answer
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What exactly happens in virtual memory when I call a function like printf in Linux? [closed]

I'm asking about functions like printf that a lot of processes might use and also need the help of kernel for stuff like system calls. What is the step-by-step description in detail for what happens? ...
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2answers
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Is the MMU inside of Unix/Linux kernel? or just in a hardware device with its own memory?

So i always thought MMU is part of the unix kernel that translates addresses to physical addresses but in the MMU wiki page it says its a computer hardware that usually have its own memory, but that ...
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Why is the transfer unit of block devices block not page?

Operating System Concepts says A character-stream device transfers bytes one by one, whereas a block device transfers a block of bytes as a unit. But I heard that the unit of transfer between main ...
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2answers
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Doesn't Linux have a special bit in the page table of processes to stop instructions to run in the stack therefore stopping overflow attacks?

So the guy in this video : https://www.youtube.com/watch?v=1S0aBV-Waeo overflowed the stack, tampered the return address, pointed it in the stack and copied the executable code in the stack with a ...
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1answer
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What's the use of having a kernel part in the virtual memory space of Linux processes?

I found a similar question but still it doesn't answer my questions Do the virtual address spaces of all the processes have the same content in their "Kernel" parts? First off, considering ...
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Memory utilization in %(Percentage) in Sun Solaris?

I would like to get the memory utilization in sun solaris system in % percentage format. vmstat 1 1 | tail -1 | awk 'a=`/usr/sbin/prtconf|fgrep Memory|awk '{print $3*1024}'{ print 100-($5/$a)*100}' ...
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Measure memory usage of forked processes

In order to measure memory usage of a process, Iam using the VmPeak and VmSize fields of /proc/[pid]/status. What happens to memory reporting if this process is forked after allocating memory? My ...
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Memory buffers usage in Linux

I have been looking at the following free -h output for a while now and trying to find out what is currently being stored in -/+ buffers/cache. Here is the free output : total ...
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2answers
233 views

What are memory primitives in Linux?

I'm reading Docker in Action and there is this sentence: Docker creates a unique IPC namespace for each container by default. The Linux IPC namespace partitions share memory primitives such as ...
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1answer
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Advantages of pageable memory

While installing a Nessus product I came up with the following statement, Generally, a Nessus Agent uses 40 MB of RAM (all pageable). Here, What they tried to mean by all pageable ? As I ...
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Pandora package for linux [duplicate]

I search for pandora package. Pandora automatically overwrites the RAM when the system is shutting down. Pandora can also be ran manually: I find something here https://github.com/Und3rf10w/kali-...
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What subsystems in Linux do their own management of physical pages?

Operating System Concepts says Two other main subsystems in Linux do their own management of physical pages: the page cache and the virtual memory system. I was wondering what the subsystems in ...
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can two running processes share the complete process image in physical memory, not just part of it?

can two running processes share the complete process image in physical memory, not just part of it? Here I am talking about the Linux operating systems(eg. Ubuntu). My thinking: I think it is ...
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File on SD card does not exists after reboot

I have a weired scenario on a Production unit. There is a SD card on the unit. I can create a file in the SD card and it shows that the newly created file exists there. I can do read/write operation ...
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1answer
32 views

“Missing” memory on ESXi VM

I’m a contractor and have been given a VM with 128 gigs of RAM which the application I’m developing needs. However, I can at most allocate 74 gigs before the allocation slows down significantly (...
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167 views

Reserve memory in RAM and in the desired physical position

I'm trying reserved 2GB in RAM, but i like reserved in the start memory, in the 0x00000000 position to 0x80000000, Can I do it? I read in the LDD3 that you can reserver spaces in the memory, but in ...
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1answer
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Understanding direct and indirect blocks?

Why can't we use use indirect blocks instead of direct blocks. Indirect blocks can store much more memory addresses which results in more data blocks. So why waste those 10 direct blocks in Inode ...
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1answer
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Available memory much lower than total while idling

I have a server where my free output looks like this: root@server:~# free -h total used free shared buff/cache available Mem: 31G 903M ...
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3answers
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What does physical address 0 in x86 Linux contain?

I am not sure if this question should go here or in reverseengineering.stackexchange.com Quoting from wikipedia: In the 8086 processor, the interrupt table is called IVT (interrupt vector table)....
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2answers
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What happens to a shared memory area when a process dies?

I'm wondering what happens with shared memory created with shmget() as shown on http://www.csl.mtu.edu/cs4411.ck/www/NOTES/process/shm/example-2.html when any of the processes terminate or die? Is the ...
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1answer
474 views

No space left on device (Ubuntu 16.04.5)

I'm really having difficulties understanding and finding out what is eating the space on my Ubuntu instance on Dreamcompute. I've installed Odoo 11 (ERP platform running on python). It works ok for ...
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1answer
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How is JVM memory usage calculated?

I am tuning my Elasticsearch cluster, and see that the memory usage doesn't line up. Running "free" on my instance: free total used free shared buff/cache ...
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0answers
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RAM not reallocatable

I have problems reallocating RAM after I've been working for some time. The problem occurs after I started/stopped various services and reached a certain limit (~16 GB out of 32 in total). I checked ...
0
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1answer
46 views

Is /proc folder and process details really exists on hard drive [duplicate]

I am a little bit confused about /proc directory. Each process frequently updating its state, memory info, progress etc in their process. My question is that the /proc directory keeps the memory or ...
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0answers
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AIX used memory gets never free

In an virtualized AIX 7.1 system when it's restarted the overall physical memory is listed as free (by all AIX stats tools). But after some hours running some applications the used memory increases, ...
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1answer
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How do I limit the maximum RAM for Linux VPS?

I rent a shared VPS that runs Debian 9. I am alloted 4GB RAM (4096MB), but sometimes my processes go over 4GB. This is largely due to the kernel caching a lot of my stuff, so I'd like to know if I ...
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1answer
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How do I use “memusage” commmand for check Memory usage of Particular program

I Want to check Memory usage of the Particular program. I'm trying to use the memusage command, as documented in its manpage which is also present in Ubuntu. But running it produces root@username:~# ...
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1answer
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How does echoing an echo not just echo in a cronjob?

I'm reading this article on clearing buffer/cache from my new Linux VMs since they're taking a full 1/3rd of my RAM, so I ran this: sync; echo 1 > /proc/sys/vm/drop_caches This immediately fixed ...
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2answers
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Memory Per Core [closed]

I am using the super computers in the network provided by Compute Canada and in the documentation page I see the following: I am quite curious - what is the concept of memory per core here? I thought ...
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2answers
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Will running a 32-bit version of ImageMagick result in half the memory usage of a 64-bit version?

I am using ImageMagick to process large TIFF images, and I am running into memory issues as the processing happens in a limited resource environment (Function Compute on Alibaba, which is almost ...
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3answers
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Linux Kernel memory management quote

I'm having an incredibly tough time making sense of this excerpt from the Linux device drivers book (sorry for text-heavy post): The kernel (on the x86 architecture, in the default configuration) ...