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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1answer
20 views
Memory Attack(Buffer Overflow) in C
Given below is the code from file q2.c
I need to use memory exploit to read the content of file 'secret' that has no read permission for my group.
I tried using ./q2 $(python -c 'print "\xad\xdd\...
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0answers
14 views
How can I prevent a single CGI script from using all 16gb of RAM?
I'm not very familiar with the code and it's already 15 years old code. It's a CGI script for an image gallery website.
Sometimes it runs 50 imageFolio.cgi-processes at the time without problems. ...
1
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0answers
7 views
Getting memory usage of a process: comparing pmap to top
I would like to get a process's memory usage and it seems that pmap can do that. However, the value it returns is different from what I see in top command.
# pmap 22080 | grep total
total ...
0
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0answers
11 views
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 ...
1
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2answers
102 views
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 ...
2
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1answer
44 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 ...
3
votes
1answer
23 views
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 ...
1
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0answers
31 views
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 ...
2
votes
2answers
43 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 ...
14
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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 ...
2
votes
2answers
70 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: ...
-1
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1answer
53 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 ...
0
votes
1answer
39 views
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 ...
0
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3answers
47 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?
...
0
votes
1answer
52 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 ...
1
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0answers
35 views
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
...
2
votes
1answer
27 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 ...
0
votes
0answers
22 views
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 ...
1
vote
0answers
15 views
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 ...
3
votes
0answers
57 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 ...
0
votes
1answer
26 views
Maximum size that can be allocated
Can I allocate more memory than VmallocTotal given in /proc/meminfo ?
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 ...
2
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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 ...
0
votes
2answers
72 views
kill deleted files and clean the memory cache
I want to know if kill the delete process , can help to clean the memory cache
sometimes we get from lsof many deleted files
so does killing them can give more available memory ?
example:
lsof | ...
0
votes
2answers
99 views
How to limit a process' memory usage while it is running?
On my server, I have a long running batch process, process_a, which have been running for several days now. I don't mind the duration of which the process needs. The problem is how process_a always ...
0
votes
1answer
95 views
Why are there no values for 'shared', 'buff/cache' and 'available' in the swap line of free?
Why are the last columns empty in the swap line?
$ free
total used free shared buff/cache available
Mem: 3912864 2255460 315388 249068 1342016 ...
0
votes
0answers
27 views
Which one to use Cross Memory Attach or ptrace?
I'm trying out ptrace system calls, I just discovered Cross Memory Attach from Christopher Yeoh.
I wonder which one is better in term of performance between Cross Memory Attach and ptrace.
Thanks in ...
0
votes
0answers
107 views
How to display `top` results sorted by memory usage by a process in KB/MB?
I have known about top command. When I using this command, I got only the memory usage of a process in terms of PERCENTAGE(%MEM) only. Is there any option to get the memory details in terms of Bytes(...
0
votes
1answer
37 views
MemAvailable higher than expected
$ free -h
total used free shared buff/cache available
Mem: 7.7Gi 4.5Gi 692Mi 305Mi 2.5Gi 2.6Gi
Swap: 2.0Gi ...
1
vote
1answer
86 views
Linux 3/1 split and physical map
I'm trying to understand the Linux 3/1 split (or 2/2, 1/3, any) and how mapping to physical memory work. Let's assume x86.
What I don't understand in particular is why the kernel's 1GiB in va[3GiB, ...
0
votes
0answers
15 views
How guarantee a responsive Desktop using cgroup memory limit
I would like to setup a system with limited memory (raspberry pi) in such a way that application can't cause the desktop (x11, LXDE, openbox, mouse driver, video card driver) to be unresponsive.
When ...
0
votes
1answer
50 views
NVIDIA usable memory 4GB instead of 6GB?
I have an NVIDIA 1060 with 6GB of memory in my laptop.
I am on Linux Mint 19.1 Cinnamon 64-bit with NVIDIA drivers version 390 official:
You can see for yourself, but I know that from Dell support, ...
9
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0answers
278 views
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 ...
10
votes
1answer
563 views
Is “Cached” memory de-facto free?
When running cat /proc/meminfo, you get these 3 values at the top:
MemTotal: 6291456 kB
MemFree: 4038976 kB
Cached: 1477948 kB
As far as I know, the "Cached" value is disk ...
38
votes
6answers
3k views
How do I use swap space for emergencies only?
I have a Debian (Buster) laptop with 8 GB RAM and 16GB swap. I'm running a very long running task. This means my laptop has been left on for the past six days while it churns through.
While doing ...
1
vote
1answer
35 views
Flashed image of full debian to larger sd card. System still full [closed]
I have debian running on a 16 GB sd card and it recently ran out of space (/dev/root is a 100%). I bought a 64 GB sd card and flashed my image of debian over to it. Even though it's running on the 64 ...
0
votes
1answer
310 views
cached memory and free command
I have a 2 cpu server running SLES 11.4 x86-64 and it has 1.5 tb of RAM.
>free -g
total used free shared buffers cached
Mem: 1514 284 ...
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votes
1answer
20 views
How do I check how much RAM a process consumes like the way `time` is used to measure the elapsed time?
How do I check the maximum amount a RAM a process uses similar to how time works?
$ time mvn package
real 0m35.796s
user 0m32.925s
sys 0m1.559s
$ maxmem mvn package
688 MB
0
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0answers
22 views
Over-allocation of memory in AIX/UNIX
Just finished my research regarding over-allocation's negative impact to VMs (Wintel).
Over-allocation - usage is 2vCPU | allocated is 32vCPU
I have not found any link regarding any negative impact ...
0
votes
1answer
63 views
Whould someone explain procstat output memory information?
I use the command procstat -r $(pidof myprocess) and I get the following output...
PID COMM RESOURCE VALUE
84867 myprocess user time 00:...
1
vote
1answer
109 views
How does the operating system read the page size from hardware?
Books on operating systems usually mentions that the page size is decided by the processor architecture, for example Intel x86 supports 4KB page size. I have a perception that when we were installing ...
1
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0answers
55 views
How can you write to the kernel memory? [closed]
During boot the kernel is loaded into memory and also in-memory filesystems like /proc or /sys are created.
How can you change values in those filesystems? Or how could you change the dmesg output, ...
1
vote
0answers
30 views
Shell Scripting best practice to make sure script is not over utilizing memory or CPU [closed]
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 ...
2
votes
3answers
178 views
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 ...
2
votes
1answer
272 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 ...
2
votes
1answer
64 views
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/...
0
votes
1answer
707 views
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 ...
0
votes
0answers
18 views
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 ...
0
votes
0answers
243 views
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 ...
0
votes
2answers
204 views
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 ...
