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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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Puzzlement on memory statistics in Linux

I am working on an embedded Linux system (Kernel-5.10.186) on a SOC platform. Now I am doing long-time testing to collect memory statistics in the system. And I had a shell script to collect memory ...
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structure /sys/fs/cgroup/memory.stat

What is the structure of linux memory via /sys/fs/cgroup/memory.stat? what is the anon memory? What is the file memory? how to get the full used memory via /sys/fs?
Irina's user avatar
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How to create a page aligned variable in a kernel module?

So I want to have a buffer in my kernel module that I created like that: static char buf[BUF_LEN]; My problem is that the start address of this buffer is not necessarily page aligned. To give a bit ...
Pinko's user avatar
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Server restarts when I run the mdadm --create command

I am not an educated computer guy, so please be gentle with me :) I have a server I use to run plex with sonarr and radarr. I am trying to create a raid array on it. I have 10x 12TB drives and I want ...
armybill's user avatar
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Setting large fs.pipe-max-size

When I increase fs.pipe-max-size like so: echo "fs.pipe-max-size = N" >> /etc/sysctl.conf sysctl -p (N is ~4-10Mbytes) And use F_SETPIPE_SZ to change named pipe sizes to N, sometimes ...
JAre's user avatar
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How to interpret the RSan memory?

From the man page of top, I found RSan is part of RES (resident memory) as follows. Private | Shared 1 | 2 ...
Zachary's user avatar
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Freeze and CPU softlock

I keep having issue with crash and softlock of my CPU. I had that with older version and still with the last update. Does someone have an idea where this can come from with this journalctl ? I use ...
Noahcode's user avatar
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How to limit ram usage of a process in Linux?

Consider a Linux process that is currently running. We want to limit the amount of RAM used by this process so that it does not interfere with the operation of the system. What tools or commands can ...
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How to prove that the eMMC on my single-board computers have a hardware defect?

Some of my single-board-computers (SBCs) are printing errors to the kernel log (dmesg) and most of the time show malfunctioning behaviour afterwards. On the same device some boots can be successful ...
mister_kanister's user avatar
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UEFI consumes >25% main memory

I just installed Ubuntu Linux 24 on a brand new Thinkpad T14s Gen 5. According to the original order, the BIOS and system data, the notebook has 16GB main memory. However, after UEFI boot, when ...
gernot's user avatar
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Grub BADRAM doesn't blacklist special memory range

I have a laptop with a damaged integrated RAM, so I ran memtest86+ to get the affected sectors and marked them as unusable. The issue came when modifying the grub configuration. I set the GRUB_BADRAM ...
Gerard Jensen Olmos's user avatar
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Understanding the “memmap” Linux parameter

I'm trying to understand the “memmap” parameter from the Linux kernel (see The kernel’s command-line parameters), in particular, the following options: memmap=nn[KMG]$ss[KMG] [KNL,ACPI] Mark ...
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Permanent brightness issue after just reading `/dev/mem`

For no reason, I've tried to read /dev/mem on a Linux x86_64 laptop using cat /dev/mem > /dev/null Under the root user, and my kernel was built without any restrictions on /dev/mem. I knew that /...
melonfsck's user avatar
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What's left unaccounted by /proc/meminfo

What is the proper formula to understand distribution of MemTotal - MemFree? On a system where Huge pages are almost not utilized I assume that it should be the sum of the following stats: page cache ...
Maksym L's user avatar
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since page table is needed to translate virtual address, how could linux kernel access and manipulate page table itself with virtual address?

According to my current understanding: there's kernel code that access or manipulate page table In kernel code, it's also virtual address used to access any struct or object, including page table ...
Qiu Yangfan's user avatar
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Why is Linux not using RAM but only Swap?

How can such an output of free -m be explained? total used free shared buff/cache available Mem: 32036 1012 225 3 8400 ...
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Understanding the reasoning behind an OOM invokation

I'm currently analyzing an OOM-killer log and there are some things that I cannot make sense of. Bear with me, I'm still new in the rabbithole of understanding the memory management in linux. The OOM ...
Noah Boegli's user avatar
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Is there a reason why sar would show different monitoring statistics on memory than other monitoring tools like dynatrace?

I'm currently investigating why I didn't get notified about a high memory utilization on one RHEL server from dynatrace. When checking the graphs of memory usage, both sar and dynatrace show different ...
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OS detects less memory than BIOS

I have OpenBSD 7.5 installed on a Beelink SER5 MAX Mini PC. The product has 16 GiB memory, and the BIOS detects Total Memory: 16384 MB (DDR4). However, OpenBSD top only reports Memory: Real: 169M/...
nalzok's user avatar
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File descriptors get corrupted when program runs in background

I have written a program for an embedded Linux system(petalinux). It runs fine when started from the terminal or TCF debugger. However, I want it to run when the system starts, so I use the start-stop-...
user3219624's user avatar
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Where is 512M RAM from?

In Virtual machine, Kali, I assigned the memory 4G, like this; But there is a problem. I installed self-build kernel at the guest to hack the memory. # uname -a Linux 15ud490-gx76k 6.8.4+ #8 SMP ...
pico's user avatar
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Is it possible to set larger buffers for file access on linux

I have a process thats reading the whole filesystem and hashing files. It slows down (by 4x or so) because the reads are causing a lot of seeking. Small chunks of each file are being read by each of 4 ...
Pete's user avatar
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Embedded Linux - How come virtual kernel memory is bigger than physical memory?

I'm running a custom Linux distribution on my ARM-based system (it's got two A7s). The Linux kernel version is 4.86.9. In the process of investigating some weird graphical glitches occuring on the ...
Frank's user avatar
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Physical memory addressing and Hugepage allocation on Linux/GRUB with x86 asymmetrical memory channels

Let’s say you have a modern AMD/Intel x86 machine with 2 DRAM DIMMs, configured as asymmetrical dual channel. One of them is 16GB and the other 48GB. In this case, I want to forbid general usage of ...
hurryman2212's user avatar
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top memory summary and process RES summation don't add up

I'm having hard time understanding memory usage reported by top. The memory summary section lists the following. All numbers in MiB. MiB Mem : 31884.1 total, 13562.7 free, 7881.9 used, 10439.4 ...
joker's user avatar
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Linux SERVER swap memory

I have a linux server. It is running java process namely kafka. I set vm.swapiness = 10. But I see the swap capacity keeps increasing, There is a lot of free memory space. Can someone explain to me ...
Tai Nguyen Huu's user avatar
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What does the "segfault at X" kernel log message mean if X is very large?

I've got a device with bad RAM. Running memtest overnight shows all faulting addresses to be in the 0x7d0000000 - 0x7f0000000 range. I plan to replace the RAM, but until then, I've disabled a 2GB ...
thariqfahry's user avatar
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How to work with CPU and memory intensive application in Linux?

This is the scenario,- it is a Java Application mainly, Heap Dump & Thread Dump is not helping me. Maybe I am not wise analyzing it. Observation 1) Lots of memory seems to be utilized. [maddipp1@...
Dev Anand Sadasivam's user avatar
4 votes
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Linux ate my RAM

I know this seems like a duplicate of many other posts in here, but I beg to differ. as this (to my not very experienced eyes) doesn't seem to be a caching problem. We have a server with 256G of RAM, ...
Forrest's user avatar
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What does Memory allocation mean?

I use Linux Mint 21.2 and my machine is Intel Core i-7 6700 3.4GHZ. I wrote a prime test in Python, and I checked it with large numbers. It is like many tests, a variation of little Fermat, so I do ...
Lereu's user avatar
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3 votes
1 answer
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How is 4kB RSS possible in Linux 4.x?

I have been the dev/maintainer of an open source IRC bot since the late 90s. The goal was always to make it as versatile & useful as possible in a small memory footprint. During the 2000s I also ...
Alonda's user avatar
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2 answers
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Is it possible to get a higher memory buff/cache usage after writing a lot of data to the disk?

On an Apache server of my own, logging requests to files has been enabled using a custom Apache module. The log files can reach several GB at the end of the day. Using Nagios I have noticed memory ...
tigrou's user avatar
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How to manually map a virtual address to a page in Linux kernel?

I am working on an embedded Linux system (kernel-5.10.24), and i am trying to do a test of mapping kernel memory. This test does similar things as vmalloc() does. It gets a virtual memory address and ...
wangt13's user avatar
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Can you mount heap onto zram

I'm new to zram, and reading the documentation it looks like it mounts something similar to a filesystem under /dev/zram<id>. If I understand correctly, anything stored here would be similar to ...
HardcoreHenry's user avatar
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2 answers
216 views

Linux disable RAM Cache

I'm running Debian stable with kernel 6.5 on an ARM M1 MacBook Air. The biggest issue is that RAM and VRAM are unified, and there is no particular way to even check how much of the used RAM is VRAM (...
Nick Bailuc's user avatar
1 vote
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Does libvirt support auto memory ballooning

I have a KVM/QEMU/libvirt Arch Linux VM running on an Arch Linux host that I use for building software. I would like it to have access to 2 GiB of RAM when it is idle, but have access to 32 GiB of RAM ...
StrongBad's user avatar
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Discrepancy between values in htop and /proc/meminfo

From the author of htops answer https://stackoverflow.com/questions/41224738/how-to-calculate-system-memory-usage-from-proc-meminfo-like-htop/41251290#41251290 I got to know that the total memory in ...
ArunJose's user avatar
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Why is Debian 12 crashing to login screen?

Situation: In the last month or two, occasionally while browsing with either Brave or Firefox I click a hyperlink and the machine crashes back to the login screen. After logging again, anything ...
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Resident memory size RES automatically decreased after 10-day aging

My application consists of multiple processes. Each of the processes has multiple threads. Heap memory areas are allocated and freed dynamically during the operation. I had a memory leaking bug in the ...
Masaki Nishikawa's user avatar
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Slow Queries, memory utilization seems low, "Database Error" messages when under only moderate load

I have a site that is set up just like the other 20 except this one is not handling database traffic like the others. It has 24 processors, 196 gig of ram. Yet under large load I see know more used ...
user2255739's user avatar
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1 answer
57 views

How does kmemleak in Linux detect the unreferenced memory?

I am working on an embedded Linux system (kernel-5.10.24), and I am trying to understand how does kmemleak work. According to the document, the kmemleak scan the data section to check if there is ...
wangt13's user avatar
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1 vote
2 answers
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System calls involved in stack and heap allocation

In the process address space, there is the stack and the heap. When a function is called, or even when a local variable is declared, it uses the stack; the kernel must assign physical address and ...
Dev Jain's user avatar
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Memory Limits (UM, UME, UMEH)

I have a system where multiple servers are all set up in the same way with the same specs. These are dedicated to processing recordings of online meetings, as well as transferring audio and video via ...
gtilflm's user avatar
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1 answer
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Why does running rsync using nohup consume all of a system’s memory? [closed]

Through both testing and plenty of examples on various stack exchanges, its clear that running rsync using nohup causes memory exhaustion, while the same rsync job running via screen or an active SSH ...
Tammer Ibrahim's user avatar
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How to read watchdog registers on x86 Linux?

I want to read the Intel iTCO watchdog registers on my Intel Lynx Point system. I found the watchdog here: [ 5598.341020] iTCO_wdt iTCO_wdt.1.auto: Found a Lynx Point TCO device (Version=2, TCOBASE=...
defoe's user avatar
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What should do to generate a minimal Linux kernel?

I am working on an embedded Linux system (5.10.24), and now I want to check what is the minimal kernel I can build, so with lots of playing of kernel configurations, now I have following kernel. # ...
wangt13's user avatar
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31 votes
1 answer
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Why is the virtual address not 4KiB-aligned when its physical address is aligned to 4KiB?

Briefly, I have a physical address inside kernel (9,932,111,872 or 0x250000000), which is apparently aligned to 4KiB (page size). When I use the kernel __va() function to get the kernel virtual ...
Ownsky's user avatar
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How can i output the result of "memusage" to a text?

When i execute a command memusage to check the memory of my program, the result is as follows. I want to output the result in the red circle to a text. How should i do?
wwb1's user avatar
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1 answer
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Which is the trigger of OOM killer, free or availaible memory in Linux?

I am working on an embedded Linux system which is on SOC platform. I have 2 machines ran the same memory workload, and I got following memory output. Machine 1. total used ...
wangt13's user avatar
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1 vote
0 answers
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Automatic Partition Resizing during Boot in Linux

I have a Linux system with a storage device containing multiple partitions. Specifically, the device (/dev/sdX) has three partitions (sda1, sda2, and sda3). The third partition (sda3) is intended for ...
Aravind Ekan's user avatar

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