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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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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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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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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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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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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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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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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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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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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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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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 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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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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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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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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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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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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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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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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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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Why there is no mc0 folder in /sys/devices/system/edac/mc

I tested RHEL 8.1, I can see mc0 in /sys/devices/system/edac/mc. I tested Debian 9.9 on the same machine, there is no mc0 folder in /sys/devices/system/edac/mc. Is that because some drivers didn't ...
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Physical address from which linux kernel is loaded

Help about CONFIG_RELOCATABLE tells : This builds a kernel image that retains relocation information so it can be loaded someplace besides the default 1MB From which I understand that if ...
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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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What is the point of the kernel reserving CONFIG_X86_RESERVE_LOW memory for the BIOS?

Since at least 2.6 kernels, Kconfig offers the option CONFIG_X86_RESERVE_LOW, described as the "Amount of low memory, in kilobytes, to reserve for the BIOS". (Starting from physical address ...
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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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What happens if a PCI device has so much memory that the BIOS cannot find a fit empty physical address region to assign it to?

A 32 bit system can have physical memory of up to 4GiB. right? Oh no, only the virtual address has 4GB limit and because the MMU can add more address bits to the page number, more physical address can ...
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Excessive Firefox CPU and RAM usage (+ choppy audio)?

I'm trying to use both Firefox Quantum 68.10.0 ESR 64-bit and TOR browser 9.5.1 (= based on said Firefox 68.10.0 ESR) on a Linux Mint Debian Edition 4 machine. What's with the resources squander of ...
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How do I reserve a large block of memory from the Linux kernel for device/DMA use?

I want to reserve a large amount (~1 gigabyte) of contiguous memory for DMA from a device. The entire purpose of this particular Linux box is to run a single application which uses the device. The ...
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How to run grep at one file in another avoiding memory exaust issue?

Have here two large text files, about 30mb each one, which would like to grep them one in another, as grep -f "file01.txt" "file02.txt" > file03.txt. Doing so returns "...
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Linux X86_64 physical memory layout

As per the Linux kernel documentation https://www.kernel.org/doc/Documentation/x86/boot.txt, there is a kernel real mode code from X+10000 to X+08000. There are two question I have; For a modern ...
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Does Pulseaudio leak memory?

I invoked the top command and got this: PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 3433 klutt 20 0 4790760 1.0g 282208 S 8.3 4.2 1261:...
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Memory watchdog for hungry applications

I have the following situation - I've got a remote PC with an encrypted drive. If the PC needs a restart, I need to be physically present to enter the decryption password because I don't have any way ...
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Memory layout and kernel space - user space

I've known that we have Kernel space and User space in a Linux system. User space is used by some specific program, and it can communicate with Kernel space with some way, for example, system call. I'...
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How are the kernel page tables shared among all processes?

I’m trying to better understand on, say, x86, how the kernel is mapped into every process address space such that changing what a kernel address maps to is able to change in all processes and all ...
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Why does “some” line have higher delay that “full” one due to memory pressure?

I have the following stats: cat /sys/fs/cgroup/user.slice/memory.pressure some avg10=0.00 avg60=0.00 avg300=0.00 total=1954777 full avg10=0.00 avg60=0.00 avg300=0.00 total=1626895 The documentation ...
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ce_count is count from kernel software or read from register of memory controller?

The value in sysfile is count from OS or read from register of memory controller? /sys/devices/system/edac/mc/mc*/ce_count I see it is counting from OS, but I think the value should be counted by HW. ...
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Sequence of events and OS involvement when a process goes beyond its allocated stack

My understanding is that the Linux kernel allocates a stack to every process before it starts, and this initial size is configurable. A process can PUSH data to the stack directly via CPU instructions,...
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Page Table Entry content when the page is in disk

Recently, I asked Page table content when the physical page we are looking for is in swap area , and for pages that are located in swap area we need to use a two-part pointer. But what happens if the ...
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Is it common to see that consecutive pages in memory are also consecutive pages of a process?

That is, we know that the consecutive pages of a process can be scattered in memory (thanks to pagination, so that there are no unused gaps). But if the OS (suppose some common Linux distribution) ...
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Need to call a script whenever edac error is thrown up by kernel/system

I need to call a script whenever the system generates EDAC errors. I created following UDEV rule for this purpose. If the ce_count changes then I would like to execute /var/tmp/test.sh, then I did ...
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What is done when memory gets filled: One page eviction or an entire process is killed?

The question is simple but I haven't found information (to be more precise, I have found information about both options (options below) but without saying which one is used in each situation). Option ...
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Page table content when the physical page we are looking for is in swap area

If this question depends on the linux distribution, please answer it in a "general way" (i.e. the most common implementation on linux distributions). In the page table of a process we can ...
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Count process L2 and L3 page faults (L3 thrashing and memory thrashing)

Right now I detect the problem by noticing that the process takes much longer than expected, killing the process and adjusting memory usage. The more time an algorithm takes the more time I waste, ...
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Can not find the process consuming high percent of memory

I have a server here wich has an alert of high memory usage (95% of all memory is being used), but i cant find where it is being used. There is the java process consuming 62% of all memory, but i can ...

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