Questions tagged [cache]

cache is a component that stores data so future requests for that data can be served faster; the data stored in a cache might be the results of an earlier computation, or the duplicates of data stored elsewhere.

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Preventing “apt-file” from updating its database with each “apt update”

Each time I run apt update or with the -m option(a.k.a --fix-missing) I see that apt-file is trying to update its cache too.I have a slow internet connection and it takes so much to download more ...
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Why is sar command rxkb/s different than iotop command's total disk write kb/s?

I'm using fio to write to a nfs mount point to test the bandwidth of my nfs server (async mount). I'm getting inconsistent results for trying to find the maximum IOPS that my nfs server can handle ...
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Free cache memory

Hi. I'm trying to free cache memory in Ubuntu. I searched several tutorials (including install bleachbit) and none of these helped me. Does anyone know how to free this cache?
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dd “direct” versus “nocache”

According to the manual for dd, there are two options that can cause I/O to bypass the filesystem cache: direct and nocache. When using these flags to, for example, copy files or copy raw data to/from ...
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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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Cleaning cache (?) command du [duplicate]

Following this question I can reproduce that the first time I execute a du of a directory it takes longer than if I do it just after. Where is this caching happening? How can I clean it? I would like ...
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Apt-file cache files location

Where are the cache files of the apt-file program ? Looks like it has some large files because it contains the information about files within all the packages in the repository (installed or ...
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How to reduce cache size for radix_tree_node?

Is is possible to reduce the space used for radix_tree_node cache in Linux without reducing overall cache size? For example, I currently have $ sudo slabtop -sc --once | awk '{ if (0 + $1 > 0) { ...
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Why does closing a file wait for sync when overwriting a file, but not when creating?

When running this script: #!/usr/bin/env python3 f = open("foo", "w") f.write("1"*10000000000) f.close() print("closed") I can observe the following process on my Ubuntu machine: The memory fills ...
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Prevent disk spinup by regular directory read access

I have a hard drive which is configured to spin down on inactivity. Unfortunately, a regularly (~every 15 min) occuring directory read access wakes up the disk from its slumber. When there is no ...
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Linux - Is it possible to create a memory filesystem (ramdisk/tmpfs) to buffer/cache data from disk?

I've got some code that processes a load of data stored on an external HDD. There is about 6.5 GiB of data on the disk, but only a few files are processed rather than the entire contents. I created a ...
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Caching executable files

Does caching executable files of apps in linux to rapiddisk improve the load time of apps? If not, can you suggest any other way to cache something that can improve the load time and performance of ...
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1answer
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USB stick shows contents of a DIFFERENT stick

I'm using Xubuntu 18.04 on a Dell XPS 15 7590. I've been having a really weird problem since I used this computer to create a bootable USB Stick so I could install Xubuntu 20.04 on a different ...
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mpv cache slowly increasing

I've recently been trying mpv as a replacement for vlc for viewing a local rtsp stream as vlc was laggy and did not stream reliably. Out of the box mpv seemed to work much better in that it streams ...
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Make Squid4 cache HTTPS GET requests

I'm following this guide for the installation with config for running sudo /usr/sbin/squid -YC --foreground -f /opt/conf/squid/squid.conf acl localnet src 10.0.0.0/8 acl localnet src 172.16.0.0/12 ...
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Why is the CPU (L1/L2) cache reported as 0kb in opensuse15.1?

When I use sudo dmidecode -t cache, I got this: Handle 0x0005, DMI type 7, 27 bytes Cache Information Socket Designation: L1 Cache Configuration: Enabled, Not Socketed, Level 1 ...
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Is there a Cache Scheduler?

I am trying to understand how Schedulers work in Linux. I am aware that there is an I/O scheduler and CPU scheduler in Linux. My question is how does Last Level Cache scheduling work? Is there any ...
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Linux and memory buff/cache and disk storage

I want to ask question about the memory buff/cache lets say we have Linux machine with disk , and some application that wrote data to disk /var/data from my understanding when application wrote ...
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1answer
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How to turn off block cache for individual processes?

I have a big system with many disk-bound services. They work much better with the usage of the block cache. Beside that, also some backup process is running. I know how should they use the block ...
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Why doesn't Linux automatically clear caches?

Background My question is basically a follow-up to this question and answer, and in particular, this comment. Whenever I have to copy or rsync large amounts of files, the memory on my system tends ...
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Automatically store based on file size - linux - bcache?

Hoping to get answers to this on Debian based distros: When saving a file, from any program, I'd wish to know if it is possible for the OS to automatically save based on file size. For example, ...
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How to disable caching for USB storage devices (by default), so that we can unplug without clicking eject?

Is there any way to completely caching for USB storage devices (I mean for example 32GB USB Hard Drives, NTFS, FAT32 formatted etc.), for Linux? (like Microsoft's Windows) People coming from MS ...
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What does 'Not Supported' mean in the msecli reports?

A Micron MTFDHAL800MCE SSD is installed on my computer system and the OS is Linux Mint18. Micron has provided msecli for the management and configuration of the SSDs using specific commands on the ...
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apt-cacher-ng with https package, release does not have release file

I have setup an apt-cacher-ng and configured it to works with https. On most https/http package apt update works. Into apt-cacher-ng server conf i added PassThroughPattern: .* and for each https ...
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How can I force yum to use just http mirrors?

I am using squid proxy for cache rpm files, and because of https urls does not cache, I have to enforce yum to use just http urls. I do not want to disable SSL Verification : sslverify=0
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Where is Firefox' DNS cache stored on Fedora 31?

I would like to programmatically clear Firefox' DNS cache from a script. Where is Firefox' DNS cache stored in Fedora 31?
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Missing bcache0 backing device

In my new Fedora 31 install there is no \dev\bcache0. The caching device is Raid 1: # ls -d /dev/b* /dev/block /dev/bsg /dev/btrfs-control /dev/bus # bcache-super-show /dev/md127 sb.magic ...
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du disk caching - why is this disk faster on one machine than another?

If I plug an external hard drive into a RasberryPi4, and run: time du -sh /mnt/disk/thisfolderis300gb.dir Then it takes about 6 minutes, all subsequent runs also take 6 minutes, But if I plug the ...
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How to free cache memory on linux without using it?

I am taking care of a k8s cluster and recently I noticed that many pods get evicted. After digging into the problem and checking the monitoring tools I found out that kubelet is considering both used ...
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1answer
243 views

Convert existing LVM LV to bcache backing device

How do I convert an existing LVM LV to a bcache backing device? The official tool for converting an existing device to bcache is blocks, but it hasn't been updated since December 2014. At a minimum, ...
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Hardware selection criteria for bcache cache device

I'm looking to buy a SSD (or USB key) for the cache device for a bcache setup. My budget is limited. What is/are the most important metric(s) when selecting a device? 4k Random read 4k Random write ...
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1answer
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How to “invalidate” or “flush” a range of cpu cache in powerpc architecutre?

I am working with an embedded device which communicates with my PowerPC CPU via PCIe. Due to the SDK constraints i have to use linux kernel version 4.1.8. This version doesn't have functions related ...
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1answer
454 views

Clearing linux caches without root privileges

In order to clear caches, I usually invoke # echo 3 | tee /proc/sys/vm/drop_caches This requires root privileges. Why do I need to do this occasionally? Because it can have a huge impact on the ...
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Linux page cache consistency

I have a couple of general questions regarding the Linux page cache. As I understand, there are (at least) three methods a block on a block device can be related to a block buffer in page cache: by ...
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Has 'sync' been proved to be necessary when writing to a block device with 'dd'?

Every time I've written a file to an empty raw block device, e.g. # dd if=image.iso of=/dev/sdb status=progress I've never used any type of sync (i.e. sync; conv=fsync; conv=fdatasync; oflag=sync; ...
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Shortcut to clear swap on demand

I am trying to make a shortcut on my desktop where i can just click on it from the Quicklauncher panel when the system is slowing down to clear the swap. Right now i am using this code in terminal: ...
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0answers
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Does linux memory cache depend on process PID?

Does Linux kernel reserve memory cache by process PID or something tied to running instance? So if I copy process memory cache to another machine, where the same application exists, but not yet ...
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61 views

How-to isolate linux process memory into a memory block device?

I have a failover pacemaker cluster with CentOS 8 as VMware VMs, which controls an application resource. This process efectively caches memory over time, so I want to replicate it's cached memory to ...
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1answer
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Which hardware is used by buffer

I know that the cache is used to store data so that future requests for that data can be served faster. Normally we have three level cache: L1, L2 and L3 in the current computer architecture. We can ...
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What happens when a file that is 100% paged in to the page cache gets modified by another process

I know that when a page cache page is modified, it is marked dirty and requires a writeback, but what happens when: Scenario: The file /apps/EXE, which is an executable file, is paged in to the page ...
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Mplayer only flushing every 256k

I am recording audio in a script in order to play it back later with a time shift. The script regularly checks if the stream is still active. Sometimes live radio streams get interrupted. In that ...
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How to determine why “target is busy” (why it won't unmount)? [duplicate]

My USB drive is refusing to unmount: # umount /mnt umount: /mnt: target is busy I believe this might be something to do with it catching up with disk caching, after some particularly intensive ...
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Awk problem in Cron VM.drop_caches=3 [duplicate]

I have some problem with the cleaning of the vm cache and AWK. I have one script who runs in cron.hourly (drop.cache) who said: sync; sysctl vm.drop_caches=3 The problem is for some reason the ...
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1answer
187 views

How to clear DNS cache on Fedora on any other Linux distro

I've just changed the hosting for my Domain the name got propagated (24 hours passed) I have new page (without SSL because I didn't added it yet on new hosting) on my android phone. But when I open ...
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Will the buff cache in Linux affect physical memory, and you don't need to manually clean up the buff cache? [duplicate]

I use free -h see this: total used free shared buff/cache available Mem: 1.9G 1.2G 157M 4.8M 630M 635M Swap: ...
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File transfers knock all the system files out of memory and slow everything down

On my desktop installation (no ssd), sometimes (sporadically) when I try to move files between drives with the Nemo file manager, the system slows to a crawl and becomes basically unusable. My guess ...
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1answer
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Removing directories not accessed in X days

I have written some scripts for downloading and caching music, and I like to delete the directories in the cache location that have not been accessed in X days. I can do that via: gfind "$music_dir" ...
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1answer
100 views

How to clear cache in Linux without flooding dmesg?

I have a shell script which repeatedly clears the cache with echo 3 > /proc/sys/vm/drop_caches The trouble is that this ends up completely flooding dmesg because it runs so often. Is there a ...
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1answer
322 views

how does the virtual memory and page cache work?

I know that: The virtual memory is split into user-space and kernel-space, and is mapped into the physical memory. When a user process accesses a file the kernel will cache the file into memory, ...
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How to reset the terminal cache in the same session properly?

Currently, I am benchmarking the running time of a package from the terminal. When I use a command with the same file repeatedly, running time was much less than the first one, and this made me think ...

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