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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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High Active(file) Memory Usage in Oracle Linux VMs

I recently searched and read lots of posts and questions about Linux memory management but I can't find my case. For example, there is a question in Unix StackExchange about High memory usage but no ...
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1answer
25 views

Kernel Logical address

Does Kernel logical address go through MMU when used in load/store instruction? Does MMU handle kernel logical address differently from kernel virtual address? Please give reasons for the same. If ...
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2answers
2k views

How to solve this memory issue gracefully?

I have a standard Linux (Debian testing) laptop, with a swap partition. I do a lot of experiments with it. Some of them are really memory hungry and the way Linux behaves by default is an issue for ...
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1answer
43 views

How to have memory/cpu limits only for forked children and not for the parent process?

Is there a way to have limits for (let's say) apache2, that limits each forked child worker process to use max X memory, and not the entire process tree (apache2 and all of its forked children) to max ...
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Find applications accessing certain memory address / trace memory access

Is there some way on Linux or Unix systems to determine if a distinct physical or virtual memory address has been accessed? I know the address or list of addresses but want to know if and what ...
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1answer
649 views

Resource (CPU time and memory) limitation and termination of a process upon violation in Linux

The problem: Given a process, limit the resources it and its child-processes can use. I.e. set CPU time and virtual memory quotas. When the process group exceeds one of the limits, terminate it, ...
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2answers
4k views

git Fatal: Out of memory, malloc failed on branch push

I know this has been asked a lot but I did not manage to get any solution to solve my problem. My coworker assigned me on a new project. The application is hosted on test Debian server with git ...
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2answers
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What's inside the kernel part of virtual memory of 64 bit linux processes?

I came upon this question : What's the use of having a kernel part in the virtual memory space of Linux processes? and based on the answer and the comments on the answer : the kernel memory ...
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5answers
4k views

Read the stack of another process?

I'm trying to read a child process's stack but with no luck. I know it is possible using ptrace, but ptrace's interface allows you to read only one word at a time, and I'm trying to scan a larger ...
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0answers
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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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1answer
2k views

How can i calculate the size of shared memory available to the system

According to the rhel document, the total amount of shared memory available on the system equals to shmall*PAGE_SIZE. After I completed the installation of RHEL6, the value of the shmall kernel ...
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3answers
665 views

Determining maximum memory usage for an extremely short process

I have a program I am testing and I need to determine the maximum memory used by the process. I know that in general ps -aux can give me this information, but the process runs in under 1/10 seconds ...
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1answer
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How large are the “watermark” memory reservations on my system?

swappiness This control is used to define how aggressive the kernel will swap memory pages. Higher values will increase aggressiveness, lower values decrease the amount of swap. A value of ...
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0answers
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What prevents page migration?

OpenSUSE 42.3, Kernel 4.4.175-89-default Running memory bandwidth intensive applications I realised the following behaviour: The application uses ~55% of the physical memory of a NUMA system with 2 ...
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2answers
7k views

Memory usage command with syntax similar to the time command

What command shows the memory usage of a program, i am looking for a command that is simple to use and has similar syntax to the time command. I am trying to find the memory usage of a md5 hashing ...
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1answer
1k views

Worker MPM or Prefork?

I understand that there is a comparison topic between the two modules but this is different. I was contacting cPanel support in order to help me freeing up some memory usage on the VPS. They found ...
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2answers
36k views

Kali won't save. Adding Persistence to Kali Linux Rolling

Normally I use my Kali Linux live usb boot using a 32gb usb stick. This time I wanted more space so I successfully wrote Kali Linux 2016 iso image onto a new 64gb stick using Win32DiskImager. I have ...
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1answer
56 views

program executing for 2 days

I have a java program which implements the Hungarian algorithm. I made changes to the existing code in such a way that the input is read from file. I have a pretty huge input around 32,000 rows for ...
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1answer
930 views

Finding the source of CoW page faults on OS X

I'm trying to find the source of CoW page faults in some C code on OS X. I would like to use the vminfo DTrace provider, but vminfo isn't available on OS X. On Linux, I can use SystemTap to print a ...
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2answers
42 views

Script to access remote node and get memory usage

I am running a large simulation on a computer cluster using 50 compute nodes. This solver uses a data structure which grows on the fly and (very) differently for each node. I need to make sure the ...
173
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12answers
139k views

How to fill 90% of the free memory?

I want to do some low-resources testing and for that I need to have 90% of the free memory full. How can I do this on a *nix system?
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4answers
3k views

If the heap is zero-initialized for security, then why is the stack merely uninitialized?

On my Debian GNU/Linux 9 system, when a binary is executed, the stack is uninitialized but the heap is zero-initialized. Why? I assume that zero-initialization promotes security but, if for the ...
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2answers
3k views

An oom killer thats baffling me

I am not able to understand why would kernel issue this oom killer when I see enough memory is available: Also why are there so many kernel cache pages allocated? I say enough memory is available ...
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1answer
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uninitialized pointers dangerous?

I read, that pointers (in C), that are not initialized, could point to an address that contain data or program code from other programs. In the book it says, that this can cause damage. Is this issue ...
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2answers
69 views

Why does RHEL use swap even when vm.swappiness = 1?

RHEL 7.2 memory use, per free -m: total used free shared buff/cache available Mem: 386564 77941 57186 687 251435 306557 Swap: ...
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1answer
259 views

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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2answers
1k views

“Wrong” total memory in VM [duplicate]

I am running here a couple of Debian 9.3 VMs with the kernel 4.9.0-5-amd64 in VMware Fusion 10.1.1 (in High Sierra). What concerns me is that the total memory in Free does not reflect correctly the ...
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1answer
897 views

How do you track memory usage in a ksh93 script

We have a number of ksh scripts that run forever (inside a while loop), or at least until a shutdown event is delivered to them. We had a project where these scripts where converted to ksh93 (and ...
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1answer
47 views

How to understand PBS output “mem” and “vmem” keep the same when the task is x-fold increased with mpirun -np x task

Here is a simple experiment I tried: Given a task called "sim.exe" which doing a model simulation, I then use MPI to launch x "sim.exe" simultaneously on one node (shared memory system). I have tried ...
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1answer
48 views

why it so important do disable THP ( transparent huge pages ) on database servers? [duplicate]

We have hadoop cluster We notice that on many DB servers, that the THPs are disabled ( include HDFS servers ) Can you explain why it is so important to disable THP on DB servers? what could be if ...
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2answers
561 views

Cgroup memory.usage_in_bytes shows incorrect value

I created a Cgroup on my Linux device and noticed that the value of memory.usage_in_bytes (4325376) is bigger than the sum of RSS, CACHE and SWAP (4194304). I read in a reliable documentation, the ...
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3answers
43 views

How to find top memory & CPU consuming process for particular time?

I have checked the sar report and found that CPU & Memory is getting utilized much more at particular time (for ex. day ago). Is it possible to find which process was taking much CPU & Mem? ...
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0answers
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Limit memory usage for a single Linux process with only a function?

This is a shell script with a function timeout() to limit the CPU time usage for a single process. Is it possible to limit memory usage for a single Linux process with a similar function? #!/bin/bash ...
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0answers
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Process only takes 50% of RAM on Debian [duplicate]

I have a program in python which takes lots of ram. My server has 16gb of ram, but when the program reaches ~8gb of ram, the os starts writing on disk which breaks performance. I want the process I'm ...
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1answer
457 views

What is kswapd_low_wmark_hit_quickly from /proc/vmstat

What does this parameter mean? # cat /proc/vmstat | grep low kswapd_low_wmark_hit_quickly 2
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1answer
961 views

“cannot allocate memory” error when trying to create folder in cgroup hierarchy

we ran into an interesting bug today. on our servers we put users into cgroup folders to monitor + control usage of resources like cpu and memory. we started getting errors when trying to add user-...
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3answers
1k views

Memory size for kernel mmap operation

I'm interested in the way Linux mmaps files into the main memory (in my context its for executing, but I guess the mmap process is the same for writing and reading as well) and which size it uses. So ...
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2answers
1k views

Questions on Linux kernel internals [closed]

I was reading "Linux device drivers, 3rd edition" and faced a few kernel items I don't quite understand. Does the Linux kernel internally operate with virtual or physical addresses? What especially ...
2
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2answers
1k views

CRON Job To Execute Command On Low Memory

I have a situation where I may need to execute an SAP command line tool hdbsql when memory gets too low (to help clean out the HANA table cache). How I can best approach this? I did have an idea to ...
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6answers
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Is there a tool that allows logging of memory usage?

I want to monitor memory usage of a process, and I want this data to be logged. Does such a tool exist?
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0answers
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Using Systemtap probing Getting the virtual address location of bytes for every read write operation in Linux

Using Systemtap probing tool I got the way to get total amount of bytes read by a file by probing syscall.read and syscall.read.return function. syscall.read.return has returnval() which gives the ...
6
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2answers
3k views

Difference between free -m and ps -euf

I have a vps machine with ubuntu 10.04 and 512Mb of RAM. I'm trying to guess how much memory is available after running the mongodb daemon. If I run free -m I get total used ...
4
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3answers
9k views

AIX memory consumption

Question: how can we report the REAL memory usage (without the cache!) using nmon or vmstat or svmon on AIX 6? nmon: vmstat: svmon: Like on Linux, we can use the free command, but it's not ...
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2answers
1k views

AIX Memory Limits

I cannot find these numbers anywhere on the IBM Web site or even random blogs that Google finds. Questions What is the maximum physical memory size a POWER7 CPU supports? What is the maximum ...
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2answers
409 views

overcommit_memory and overcommit_ratio

Here is my current setting: vm.overcommit_ratio = 50 (default) vm.overcommit_memory = 2 And Current Memory Usage: [localhost~]$ free -g total used free shared ...
4
votes
1answer
1k views

Reliably determine free memory

Linux distributions tend (but are not required) to include free from procps, which allows a nice concise display of memory consumption: # free -m total used free ...
2
votes
1answer
1k views

why centos7 free command output available value less than free value

I ask a question, In my centos7, why available value less than free sometimes I think available value is equal to free+buff+cache, available means when start a app how many memory can use? [root@...
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1answer
25 views

Maximum size that can be allocated

Can I allocate more memory than VmallocTotal given in /proc/meminfo ?
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0answers
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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 ...
3
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2answers
69 views

Reading and writing data temporarily without using the filesystem

I'm using ansible in a vagrant environment managing a debian box. Due multiple ansible provisioners with vault encrypted data (e. g. database root password) I have to enter the vault password once by ...