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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How do I delete shared memory that was used by mounted tmpfs directory?

I executed this command to create a RAM-Disk: mount -t tmpfs -o size=60G tmpfs /tmp/ramdisk After that I copied several files into this virtual filesystem as follows: cp /mnt/user/hugefile.bin /tmp/...
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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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Why does disabling Kernel Page Table Isolation decrease MemTotal?

Iso kernel (Linux 5.4.60), Iso hardware, Iso config apart from case A: CONFIG_PAGE_TABLE_ISOLATION=y and, case B: CONFIG_PAGE_TABLE_ISOLATION=n iomem reports an identical map (apart from Kernel code ...
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High IO rate when the system out of RAM

I found that when the system goes out of memory, the disk IO usage will be very high. It seems many processes are reading from hard disk frantically (check htop output below). When I kill a process ...
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1answer
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Hardware information with Debian 10. How to determine RAM clock speed

Are there any tools to determine current memory clock speeds on Linux systems? (Specifically Debian 10.) From my searching so far I am aware of dmidecode, but this does not report true current ...
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Loading executable object files and creating private area

I was reading a textbook on virtual memory and it says: Any Linux program can invoke the loader by calling the execve function which does: Delete the existing area structs in the user portion of the ...
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Linux, at what point a device can write to the main memory through DMA?

I am trying to figure out how and when Linux gives the permission to perform direct memory access (DMA) to the peripheral devices on PCIe. I have read how DMA is initiated in the kernel's "DMA ...
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How to deallocate Linux RAMdisk

I am having trouble to deallocate RAMdisk in Linux. I think that blockdev --flushbufs /dev/ram0 used to work in the past. But now: cat /dev/urandom > /dev/ram0 md5sum /dev/ram0 ...
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How are page tables generated by the operating system, per process? [closed]

I know each process has it own virtual address space. A table is generated per process to map the virtual address to a physical address which resides in physical memory (called pages). When trying to ...
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Cannot allocate memory

I'm trying to do MRI analysis with FreeSurfer's last version. But it cannot complete the process anymore. 3d normalization pass 1 of 2 white matter peak found at 110 Cannot allocate memory Linux ...
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How to find hugepage size on system?

I am getting following two different result. which one i should consider for Hugepage? [root@server ~]# getconf PAGESIZE 4096 [root@server ~]# grep -i hugepagesize /proc/meminfo Hugepagesize: ...
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What's the use of having a kernel part in the virtual memory space of Linux processes?

I found a similar question but still it doesn't answer my questions Do the virtual address spaces of all the processes have the same content in their "Kernel" parts? First off, considering ...
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How to see buffered and cached data

~$ free total used free shared buffers cached Mem: 3891076 1044972 2846104 0 82744 463876 -/+ buffers/cache: 498352 3392724 ...
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Address of a PCI device obtained from lspci -vvv is invalid?

I try to read a PCI device memory area (I know at what offset from that device is stuff I look for) so first I try to obtain the system memory address where that PCI device memory has been mapped. In ...
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1answer
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Where does the Linux kernel reside in memory ?

From some book I have, I have in my notes that the Linux kernel resides at 0xc00000000 on 32-bit systems, and is mapped into user space for performance reasons. Is this accurate ? How can I verify ...
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What do the “buff/cache” and “avail mem” fields in top mean?

Within the output of top, there are two fields, marked "buff/cache" and "avail Mem" in the memory and swap usage lines: What do these two fields mean? I've tried Googling them, but the results only ...
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Differences between swap part in top command vs swap -l command

I have a system running with 256Gb RAM. My swap space is getting exhausted due to some process. So as a diagnostics, we put a crontab to monitor the usage and space. This is where I am confused. The ...
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Filelight /home in /usr/share

I needed to remove some files in / and I noticed I have a folder /home/myusername in /usr/share whereas no such folder appear when I list the directoty, symbolik link or else in /usr/share. What could ...
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Syntax for memory request in a Sun Grid Engine job file

I'm submitting a Matlab job in the cluster of my university using qsub after having logged in a node using ssh. The job runs out of memory. This is the advice I received to fix my issue: "...
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How to run an app on memory in a untrusted computer?

I'm having complex situation where I would like to run an application without adding into Hard Drive to prevent unauthorized copying during a demo. Is there are any tool on Linux that I can use to run ...
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1answer
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Get memory type and speed without sudo

On CentOS, lshw and dmidecode can tell you memory type (e.g. DDR3) and speed but need sudo or root. Looks like /sys/devices/system/edac/mc/mc*/dimm*/dimm_mem_type has the memory type info but not the ...
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Allocate more memory and cpu resources to a program

I am running unzip to unzip huge files. However, my cpu usage is under 15 percent and ram is only utilizing 1-1.2 GB out of 8 GB. Is there a way to allocate more cpu power and ram to this unzip ...
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Linux memory usage does not add up

I have a server for which I cannot account where the ram is going. Output of top (sorted by %MEM) indicates I have 96GB of ram on this server. top - 23:30:54 up 1 day, 21:55, 2 users, load average: ...
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How to get reports from kswapd, like, why it was triggered, what it did with what results?

Is there a way to obtain information about kswapd operation, that is: a) what was the reason it was triggered, b) what did it actually do and c) what were the results of its operation? Background: ...
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Why two linux systems has different memory usage for same processes?

I have a desktop and a laptop running Arch Linux. Both have Intel i3 process, desktop with i3 3rd gen, while the laptop runs i3 6th gen. Both have 4 GB RAM + 4 GiB ZRAM. But I have seen that the ...
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How EDAC get error notification? from BIOS or memory controller?

We use EDAC to monitor errors on DIMM. I would like to know how EDAC gets notifications about these errors? The memory controller has interrupt to notify BIOS, then BIOS notify OS? The memory ...
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How to limit application memory usage?

I have spend 2 hours reading questions about this matter, and still there is some misunderstanding. I have this process: USER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND root 1452 0.4 1.8 ...
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how to check memory usage, in detail

There are commands such as top, ps, pmap (and others) that show how much memory is used by a process, but they only show the total memory. Using the free -g command output we see total, used, shared, ...
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Is there a way to limit the amount of memory a particular process can use in Unix? [duplicate]

I need to test a process for memory management. I do not have the source, so I need to do all the testing from the OS side. I want to be able to say something like limitmemory 400k -p <pid> Is ...
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1answer
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Do linux also have nonpage memory?

In Windows, we can find non-page memory and it was used for kernel and driver. ( in my understanding ). Does Linux also have non-page memory? In my understanding, for every byte of memory, it must in ...
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1answer
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I want to know how to quickly reset(clear) eMMc(SD). (dd is too slow!)

I am using an embedded board. I am using eMMc(8GB) as a boot device.(I also use SD cards.) I think I need to reset the boot device if I reinstall the OS. So I tried reset with the following command. ...
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What is the “thundering herd” problem and how can a race condition happen even after using spinlocks?

From here: wait_table A hash table of wait queues of processes waiting on a page to be freed. This is of importance to wait_on_page() and unlock_page(). While processes could all wait on one queue, ...
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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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How do I use “memusage” commmand for check Memory usage of Particular program

I Want to check Memory usage of the Particular program. I'm trying to use the memusage command, as documented in its manpage which is also present in Ubuntu. But running it produces root@username:~# ...
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SIGBUS immediately after successful mremap for shared memory

I am using POSIX shared memory. Initially I map four shared memory buffers. One of them exceeds its allocated size so I call mremap: void * remap_shm(void *old_address, size_t old_size, size_t ...
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1answer
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Linux (RHEL) problem with cached and swap memory

I have a problem with linux cached and swap memory. I know that linux is optimising itself when reading data from the disk (buffering it in the RAM) but in my case it seems that this part of memory is ...
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1answer
638 views

Discrepancy between physical RAM and /proc/meminfo

I have a system with 8 x 16 GB DIMMs, so 128 GB total. However, the MemTotal reported by /proc/meminfo is 131927808 kB, so 131 GB My research suggests that if anything, the meminfo should add up up to ...
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1answer
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what does mean by HardwareCorrupted, DirectMap4k, DirectMap2M fields in “/proc/meminfo” file of Linux?

I am looking for description of following terms: HardwareCorrupted, DirectMap4k, DirectMap2M fields in "/proc/meminfo" file of Linux. I could find the following description for the fields ...
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3answers
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What is using a 1G-byte page on my system?

I have noticed that if I do cat /proc/meminfo I get the following … HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB ...
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1answer
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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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Buffer Memory Drops to Zero

We have been having problems with a system that becomes inaccessible. Characteristics are 1) sudden spike in blocked and run queues and 2) buffer memory drops to zero. The symptoms are 1) existing ...
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About mem and vmem

I am working with a cluster machine running under linux. I have a shell script that uses mpirun to submit my jobs to the cluster machine. In that same script, I can choose the number of nodes that ...
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1answer
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Do sync and writing to /proc/sys/vm/drop_caches really empty all the disk cache/buffers?

When you want to empty disk caches/buffers, you usually issue the following command: # sync && echo 3 > /proc/sys/vm/drop_caches But after typing that command, free doesn't really report 0 ...
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What are high memory and low memory on Linux?

I'm interested in the difference between Highmem and Lowmem: Why is there such a differentiation? What do we gain by doing so? What features does each have?
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How can I test the RAM for data corruption on an ARM-based system?

I have an embedded device. It is ARM based, with Linux 2.6.31 and has 256 MB RAM. I wanted to get some ideas/tips on what is the most effective way to test the device RAM for data corruptions. Is ...
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Will hibernation to swap partition automatically fall back to swap file when swap is smaller than RAM?

I'd like to understand how the hibernation process works in Linux, with regards to memory size and swap. Is hibernation limited to swap partition size? What does it do when RAM doesn't fit? Consider ...
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1answer
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How can I trigger Firefox memory cleanup from the terminal?

Does anyone know how to initiate the garbage collection and memory reduction in Firefox (about:memory > Free memory > GC/CC/Minimize memory usage) from the terminal? This browser is using way to ...
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1answer
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No space left on disk (PostgreSQL)

I was trying to write a 55GB SQL file to my database. It used to crash each time. I removed logs and did some cleaning to get the server running, but the transaction never used to complete. Latter, I ...
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1answer
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Available memory drops with usage, and closing applications/restarting X doesn't regain it

I'm aware that the kernel uses memory for caches, but that that memory is available to user applications on demand. In claiming that memory is "missing" I am refering to the "available&...
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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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