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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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Why can't I “swapoff” when there's plenty of memory?

I've recently noticed that even though there's a lot of memory on my system: # free -m total used free shared buffers cached Mem: 15965 9680 ...
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831 views

What does hierarchy support do in cgroup?

cgroup has 2 options for memory control: memory.use_hierarchy = 1 : use hierarchy memory.use_hierarchy = 0 : use flat hierarchy, according to this answer What is the difference between the two? I ...
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11 GB of GPU RAM used, and no process listed by nvidia-smi

In my GPU #0, 11341MiB of GPU RAM is used, and no process is listed by nvidia-smi. How is that possible, and how can I get my memory back? Thu Aug 18 14:27:58 2016 +-----------------------------------...
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Why does /proc/*/status not account for all swap used on a system?

I have a system that has been swapping recently and am unable to account for all swap that is shown as in use by tools like free or top. Specifically, I can account for 19GB of 28GB swap used (...
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1k views

Process killed by OOM killer when plenty of memory apparently free

I'm working on an embedded ARM-based platform. 32-bit, 512MB of RAM, no swap. Linux 3.10.53 (some variety of Ubuntu, if that's relevant). Some code I'm working on is getting consistently oom-killed, ...
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593 views

Memory consumption over variable period of time

There are a number of questions on this StackExchange about memory consumption, notably: How to check which process is using most memory How to display top results sorted by memory usage in real ...
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837 views

How to read the output of the show-memory-usage SysRq?

I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it? Here is an example output form my box (Kernel ...
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2k views

is THP good or bad for MySQL Server?

Linux kernel new feature called Transparent Huge Pages (THP) which is by default enabled on CentOS 6.x and above OS. Is THP good for MySQL DB machine? I am trying following to disabled THP but seems ...
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242 views

Understanding main memory fragmentation and hugepages

I have a machine that is intended for general use and which I also used to run a QEMU virtual machine. Because the virtual machine should be as performant as possible, I want to back the VM memory ...
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794 views

kernel: pci 0000:7f:12.4: BAR 3: failed to assign [mem size 0x00000010]

My host machine is always stuck recently. and sometimes also black screen. And when I start my host machine(CentOS 7.2), it records those information in the /var/log/messages: The logs is below: ...
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Are there any tools to test MTD/JFFS2 for Linux 2.4 kernels

I have some issues with a platform I support and I suspect memory problems. I wanted to check the Flash parts using some MTD JFFS2 test tools, I found a link to a bunch on this site. However they ...
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56 views

Cannot change memory protection

I have a tricky problem with memory protection. I am not able to start some programs because of the problems with some libararies. I run into a "cannot change memory" issue. I mapped the user home to ...
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416 views

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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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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377 views

Centos 7 stopped detecting all RAM on system?

After months of working fine, the BIOS for my Centos 7 installation suddenly maps the wrong amount of memory to the kernel. I have 8 GB of RAM installed and the SO only maps 3.2 GB of RAM. I can't ...
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575 views

Total available physical memory from /proc/meminfo not adding up

I'm trying to account for the available physical memory on a Linux box through /proc/meminfo (output provided below). Accounting for current free memory, user-space physical usage, kernel data ...
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53 views

Entire Harddrive to linux swap

I have an old hard drive that is less than 50Gb and a computer that only has about 4Gb of ram (and ~250Gb main HDD). I was thinking about using the second drive as an entire drive linux-swap partition....
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616 views

Possible slab memory leak related to bio and btrfs?

I'm currently running a rebuild on a btrfs NAS (~20TB) that had a drive failure. It's going to take a few days. My problem is about once every 24 hours the RAM filled up and the kernel starts killing ...
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174 views

Any way to specify process to call on Linux when OOM activates?

On my embedded system I'd like to record when the system OOM killer actives, e.g. by setting an env. variable in u-boot. Is there any way to specify a hook function to call on the OOM event?
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1k views

Boot rescue kernel at high memory address using kexec on arm

Summary: Crashkernel boots at 512MB address in RAM with kexec -e/-l but not with kexec -p - why? Embedded platform with Marvell Armada XP (MV78460) (ARMv7 with 4 cores) and 1GB of RAM. production ...
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65 views

Which parts of Memory can Swap Support

For this question, "swap" does not include RAM and only refers to the configured space on the disk. According to, http://www.ualberta.ca/CNS/RESEARCH/LinuxClusters/mem.html, a program's memory usage ...
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434 views

Limit system processes using cgroups

My server runs several dozens of processes that are not in my control (mostly monitoring software). According to my application logs, sometimes some of the third party processes try to allocate too ...
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789 views

Why does saving a KVM-QEMU VM requires additional memory?

I have three VMs running on Red Hat Enterprise Linux with 8 GB RAM, each of the VMs has 3 GB allocated, and I also run a 512 MB VM. If we also consider the guest OS's memory usage (usually 1.5 GB due ...
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217 views

Cgroups - memory subsystem

I want to set the memory.limit_in_bytes parameter for a control group and disable OOM, so processes freeze when the limit is reached. That said, I want to change that limit dynamically based on ...
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0answers
1k views

What is the structure of Libvirt Qemu VM dump/save files?

I need to do some exploration of Qemu-KVM virtual machines physical memory (particularly I need to check the fact of the physical memory intersection). In order to do that I'm trying to save VM's ...
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366 views

Why message queues are not being used for any system level applications in Ubuntu OS?

In my Linux machine, when i run 'ipcs' command, I have the below information listed srinivas@srinivas-G41MT-S2:~$ ipcs -a ------ Shared Memory Segments -------- key shmid owner ...
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481 views

VMO Changes After Adding New RAM To AIX?

We have a server at a client site running AIX 5.3, which we just up the RAM to 32GB, from initially 16GB (if I'm not mistaken). This server is our Application server running J2EE applications on top ...
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0answers
1k views

Linux kernel slab usage growing on embedded system

I'm in the process of QA/debugging a project on a custom embedded linux system. The problem we're VERY tight on memory, and even a couple megs can cause issues with our software. What I'm seeing (...
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0answers
14 views

Allocate pools of hugepages separately on each NUMA doamin

On my dual-socket machine, I'm trying to allocated two pools of hugepages (one for each socket), so that the application A, which is pinned on the first socket, uses the first pool, and the ...
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0answers
208 views

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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106 views

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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0answers
51 views

How can I get information about TLB memory on macOS

How can I get information about TLB cache memory on macOS? Things like number of entries, associativity, covered page sizes. I have tried to using tools like cpuinfo_x86 but it doesn't prompt much ...
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0answers
758 views

Slab cache affecting used memory much more than /proc/meminfo suggests

I'm dealing with a memory issue that is affecting hundreds of machines in AWS. They are i3.4xl instances with 120GB of RAM. There is a Java database server running inside a Docker container that ...
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0answers
202 views

alloc_contig_range test_pages_isolated failed

On an embedded linux system (arm cortex a9 imx.6), the hmi program froze at a certain time. At the same time there was the following log in /var/log/messages es well with "dmesg": alloc_contig_range ...
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57 views

How do I reserve a range of page frames just for my kernel driver?

I have a specific set of page frame numbers (PFNs, memory) that I want to reserve for my kernel driver. How do I do that? Can I do it at boot time? Any pointers appreciated.
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1k views

Why doesn't Ubuntu see all the memory I have installed?

How can this be: $ sudo dmidecode -t memory [sudo] password for dims: # dmidecode 2.12 SMBIOS 2.6 present. Handle 0x0008, DMI type 6, 12 bytes Memory Module Information Socket Designation: ...
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263 views

Limit imagemagick resource consumption

Imagemagick's convert -list resource lists the resource limits for imagemagick processes: File Area Memory Map Disk Thread Throttle Time ----------------------------...
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0answers
307 views

Why the output of “free” is different from summation of memory usage for each process in “ps”?

I have a Redhat system which has a total of 64GB RAM. As per free output it is utilizing 47GB of RAM. free -g total used free shared buffers cached Mem: ...
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0answers
358 views

How do I figure out what is consuming memory?

I develop a system (x86_64 based) that runs Linux (Ubuntu 14.04.3) and has several pieces of custom built hardware connected. I have written drivers and control software for the custom hardware. ...
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0answers
465 views

Creating CPU/GPU/Memory load average history

In our research group we are running a computing server for deep learning with a number of NVIDIA Titan X graphics cards and quite some CPU cores. Given that it is a research lab and we have ~10 ...
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0answers
363 views

Is there a more efficient way of defragmenting Linux memory other than rebooting?

I am running Gentoo Linux with kernel 4.4.8-hardened-r1, QEMU-KVM version 2.5.1 and 3227 MB of system-visible RAM (without considering RAM taken by BIOS and my AMD APU's graphics). I have a VM that ...
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0answers
583 views

GNU/Linux OOM (out of memory) freezes - solution ideas

Explanation While working with older machine with swap on and 2 GB ram, I frequently encounter behaviour well described as freeze: here, what is the best way to prevent out of memory oom freezes on ...
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0answers
361 views

OOM Killer: Processes have a score of over a 1000

All top links when Googling for OOM score seem to indicate that the values must be between -1000 and 1000. I tried to verify that with a simple cat /proc/*/oom_score | sort -n | less and I ...
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0answers
130 views

What does it mean when a private VM page is none of `rwx`?

UPDATE: It's a padding: every such non-rwx area is preceded with a readable and/or writable area and together they constitute a 64Mb segment (for 64bit architecture). A relevant question on SO: ...
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0answers
1k views

Portable way to parse /proc/meminfo

I'm having trouble finding a generic code that work, here, for both CentOS 5/6 and CentOS 7 versions pc the /proc/meminfo file. I Want to compute the "Real Used memory" like free does. (amounts ...
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0answers
1k views

Java process gets killed frequently by OOM - Killer on upgraded hardware

I am running solr on an Ubuntu server along with 4 other java processes. Current index size is 30 GB. My solr process gets killed frequently in few hours. It clearly mentions that its an OOM killer. I ...
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0answers
836 views

How can the RES memory reported for a Java process be higher than the VIRT memory?

I've been monitoring a Java process (Oracle Weblogic) using TOP and have observed that sometimes the following will happen: RES will increase from it's usual stable level of 2,097,152 KB up to almost ...
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0answers
89 views

What uses Linux “application memory”?

Just for fun, I wanted to watch what ls -lR / does to my "buffers" memory on a Linux system. As expected, the value increased. But I noticed that the "application memory" (i.e. "used" - (buffers + ...
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0answers
4k views

Increasing ulimit stack size benefits?

Hello I'm new in Linux and at my work I have a server that runs a banking software. The company that made the software said that the stack size should be set to unlimited. Does this make the software ...
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0answers
180 views

Getting non-stored password from Icedove

I've recently changed my mail password (because of Heartbleed), but I've forgotten the new one. When entering the new password in Icedove, I didn't think of clicking "remember password", but the ...