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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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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3answers
29 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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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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0answers
23 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
...
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0answers
11 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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0answers
21 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 ...
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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 ...
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0answers
40 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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1answer
25 views
Maximum size that can be allocated
Can I allocate more memory than VmallocTotal given in /proc/meminfo ?
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2answers
63 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
13 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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2answers
42 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 | ...
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2answers
61 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 ...
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1answer
65 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 ...
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0answers
22 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 ...
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0answers
38 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(...
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1answer
23 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
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1answer
78 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, ...
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0answers
12 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 ...
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1answer
49 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, ...
8
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0answers
161 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
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1answer
518 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 ...
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6answers
2k 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
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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 ...
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1answer
150 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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1answer
19 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
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0answers
21 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 ...
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1answer
56 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:...
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1answer
66 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
44 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
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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 ...
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3answers
162 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 ...
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1answer
173 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
49 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/...
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1answer
464 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 ...
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0answers
15 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 ...
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0answers
214 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 ...
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2answers
140 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 ...
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0answers
235 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: ...
2
votes
1answer
54 views
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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0answers
7 views
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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1answer
22 views
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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votes
2answers
46 views
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 ...
1
vote
2answers
40 views
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
348 views
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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0answers
36 views
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
...
2
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0answers
173 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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0answers
24 views
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 ...
0
votes
1answer
79 views
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 ...
3
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0answers
48 views
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 ...
