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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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Shell Scripting best practice to make sure script is not over utilizing memory or CPU [on hold]

I have been writing shell scripts from long time but I never thought of optimizing script to make sure its not using more cpu or memory .. I am looking out for some suggestions or process with which I ...
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how to know the right swap size for hadoop Linux machines

we are using many hadoop clusters for now we are using swap size - 16G free -g total used free shared buff/cache available Mem: 125 ...
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Why does swappiness not work?

We have a RHEL 7 machine, with only 2G of available RAM: free -g total used free shared buff/cache available Mem: 31 28 0 ...
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1answer
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Access grab state of evdev device

I need to retrieved the grab state of an evdev device in a program. More specifically, I need to retrieve the state of the grab pointer in the evdev struct seen here: https://elixir.bootlin.com/linux/...
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Compiled kernel 4.19 will not boot: “Kernel panic not syncing : System is deadlocked on memory”

I am compiling kernel 4.19 on Ubuntu 14.04 because I have a assignment to add a system call, but when I try to boot this kernel there's a error: Kernel panic - not syncing: System is deadlocked on ...
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How to measure the memory used by a process at SIGABRT?

I run a long compilation that uses lots of memory. At a point it fails with SIGABRT. I would like to know how much memory is used then, before shutting down the process. I use CentOS. Is it possible ...
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Input/Output error after moving files on external hard-drive

I have an external hard-drive for saving all my photos/memories. I put all the pictures to the folder INTENSO/Handy-Backup/IPhone/DCIM/. Because I resetted my iPhone, I wanted to move all the old ...
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Why /proc/meminfo shows MemAvailable under Kernel Version 3.10?

I've been using CentOS 7 and its kernel version is 3.10. To check Kernel Version, I typed 'uname -r' and command showed 3.10.0-957.1.3.el7.x86_64 As far as I know, MemAvailable metric was introduced ...
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Kernel BUG: unable to handle kernel paging request

So I'm trying to run this kernel module on my laptop, and every time I do so, I get a stack trace that looks like this (all the messages might not be relevant to the module). [17539.035247] EBBChar: ...
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What happens to memory that wasn't freed in a kernel module after unloading?

Suppose I called kmalloc and didn't free that memory before rmmod was called on the module, what happens to that memory? Is it a memory leak and it is completely unusable until restart, or does the ...
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Resources used in sync operation

When we are performing sync operation to transfer buffer cache to disk. What kind of resources will be used the most from CPU, memory or disk? and how?
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Are files always cached in $BLOCKSIZE increments?

Given a 4KB block size, when a 1KB file is read from disk and cached in main memory, is the entire 4KB block that contains the file cached? Similarly, if opening a 100KB file, seeking 50KB in and ...
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Does the bootloader load the kernel fully into memory

I read that the bootloader (Grub, or U-boot etc. ) locates the kernel (from maybe the HDD, or even flash memory if it's an embedded system) and loads it into memory on startup. Now, does this mean ...
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2answers
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compare memory performance of two machines (low buffers vs high cached)

I'm trying to compare the performance of two machines that I have. I have in both of the machines a database that was installed with the same settings. Both of the machines have the same amount of cpu(...
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2answers
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How to get value of a memory address using command?

At the memory address, 0x7fffffffeb58 of a program lies a value, I want to find out the value of the address. Is there a way to get the value just by using commands? I've tried dd but to no avail.
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Cache behavior in dd command

I am performing some dd outputs and running in parallel vmstat: With no direct write (i.e. via cache) $ dd if=/dev/urandom of=somefile.txt bs=1M count=200 200+0 records in 200+0 records out ...
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Memory dump on Ubuntu 18.04 failed on too big /proc/kcore/

There are two great articles about how to aquire memory on Linux using linpmem: SANS holdmybeersecurity Trying the approach from holdmybeersecurity I ran into the following issue, which seems to be ...
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Finding usage of “buff/cache” (as mentioned in free)?

When I run free, I see free -h total used free shared buff/cache available Mem: 15Gi 1.7Gi 4.3Gi 149Mi 9.5Gi ...
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1answer
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httpd hogging all memory until server crash

The server in question is used for processing data into reports, it has three cron jobs which execute every minute to check the process queue and if anything is found they'll keep running until the ...
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0answers
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What are the differences between process data segment and resident set size? [duplicate]

I searched how to limit memory usage for a single process and found 3 results,ulimit -d, -m and -v, which stand for data seg size(process's data segment), max memory size(resident set size) and ...
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1answer
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Sum of cached memory and shared memory exceed total memory [duplicate]

When I run free -h, I get: total used free shared buffers cached Mem: 251G 208G 43G 179G 144M 190G -/+ buffers/cache: ...
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2answers
58 views

Check which process is using most memory and summary total used memory

by the following command we can check which process is using most memory as we can see the first field show in MB the used for each process is it possible by awk to sum all the numbers and to get ...
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How to read/write system RAM via physical address [duplicate]

My system is based on x86(64-bit) and it has 8GB RAM. I have set reserve 100MB of 8GB using memmap=100M@0x40000000. For this way does it guarantee to reserve the 100M of RAM? Can I access the 100MB ...
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Best way to get precise measure max memory usage and cpu time [duplicate]

I need to test huge amount of applications that will run mostly about 100ms to 1s(pretty fast). I need to measure max memory usage and cpu time on each of them. because they fast I can't just check ...
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Script that displays information about most used processes

my script is `echo 'CPU:' | ps -eo pid,%cpu,pmem,vsz,time,command --sort=-%cpu | head -1` echo 'VSZ:' | ps -eo pid,%cpu,pmem,vsz,time,command --sort=-vsz | head -1 but I dont know how to write the ...
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How can I print the memory usage in KB by free?

I need to print the RAM memory used at this time in kilobytes(KB) with command free, how can I do that with one line command input: free ... output: 567595 output should be contain only kilobytes ...
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SYSV shared memory object has more blocks allocated than its size? [duplicate]

I found some weirdness in the file size of SYSV shared memory objects, when I was looking at firefox. For some files, blocks * block size is greater than the file size. Isn't this impossible? How ...
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2answers
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Can I see the amount of memory which is allocated as GEM buffers?

My /proc/meminfo shows about 500 MB is allocated as Shmem. I want to get more specific figures. I found an explanation here: https://lists.kernelnewbies.org/pipermail/kernelnewbies/2013-July/008628....
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1answer
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/proc/meminfo says VmallocUsed is 0. So where are my kernel modules stored?

I thought the code for kernel modules was stored in a vmalloc() allocation? (In fact I'm sure the kernel code is using vmalloc(), not kvmalloc()). So why does /proc/meminfo say I have no zero ...
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1answer
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What's causing dbus-daemon to take up over 3GB of RAM?

dbus-daemon is consuming a lot of memory on my Debian 9/KDE machine. How can I find out why? The amount of allocated RAM is not changing anymore: it's stable at well over 3GB. I already tried closing ...
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1answer
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Can you edit address values in “/proc/$pid/mem” to reflect changes in that process?

I would like to see if I can edit a value in my program while it is running by directly changing the memory. My thought process (untested) is to do the following: Run the program. Open up "System ...
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1answer
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Memory immediately available in linux memory management system

This is the output of free -h command on my Ubuntu 18.04 laptop: $ free -hg total used free shared buff/cache available Mem: 11G 4,2G 3,4G ...
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How to know the profile of a Linux memory dump with Volatility? [closed]

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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2answers
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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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1answer
161 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
58 views

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
38 views

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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0answers
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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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0answers
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Where else could memory be used other than process, cache and tmpfs? [duplicate]

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. How can I free this stuck memory ...
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1answer
25 views

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 ...