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Unix & Linux

Questions tagged [cache]

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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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I'm running Debian 13 (fresh install) and want to use specifically Nextcloud and Immich on docker on an SSD and 2 HDDs with 10TB for data (and the second for raid/snapraid or backups or similar). For ...
mike's user avatar
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My system has 64GiB of memory. I noticed it usually uses about 20GiB for cache. I wonder if I do "suspend to disk", does the cached part get dumped to disk as well, or is it written to disk ...
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I only recently "discovered" the inline_data feature of ext4, although it seems to have been around for 10+ years. I ran a few statistics on various of my systems (desktop/notebook + server),...
Mike's user avatar
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I am using an lvm cache in the most usual combination (small, fast ssd before a huge, slow hdd). It is simply awesome. However, I have not found a way to know, how many blocks are actually cached and ...
peterh's user avatar
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Test environment: Virtual Machine(Windows 11, VMware Workstation Pro), Ubuntu 22.04, mechanical hard drive. Use the following command to generate 1GB of test data: dd if=/dev/urandom of=test.data ...
沈小伟's user avatar
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I'm working on a C++ application on Ubuntu 20.04 that uses PCIe DMA to transfer data from a user-space buffer to hardware. The buffer is mapped to a fixed 1K physical memory region via a custom ...
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I have a large slow HDD and a small fast SSD. This is about reads not RAID. My desktop grinds to a near-halt when switching back to Firefox or man pages after (re/un)-loading 12+ GiB of Linux kernel ...
Daniel T's user avatar
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About GPG is mentioned the gpg-agent and I read the following answer: gpg does not ask for password Where is mentioned the --default-cache-ttl and --max-cache-ttl options. So I found this official ...
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I have a project where I need to get the size of the cache on my Linux machine. I don't know the linux distro, and the /etc/os-release file does not exist. I only know the kernel and architecture: ...
Plat00n's user avatar
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I've been running a new Synology RS3621RPxs for several weeks, and my 4TB SSD cache shows: Cache composition: Reusable (341 GB) / Total (3.6 TB) If I'm reading that correctly, my nas isn't even using ...
TSG's user avatar
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I have a new Synology NAS with 2 storage pools, and I have one volume per pool. I have added a single SSD to the NAS to serve as a cache, and was able to add it to the first storage pool. This is a ...
TSG's user avatar
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I know that recently accessed files are cached into the RAM, but is there a cache for frequent commands? For example, if I run cat file.txt multiple time, file.txt will be cached after the first ...
glacier's user avatar
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I am working with a remote parallel file system (CephFS), mounted at /mnt/mycephfs/, which contains a large dataset of small files (200 GB+). My application trains on these files, but reading directly ...
H.Jamil's user avatar
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I was forced to change ssl certificate for one from my domains. So, cert changed, sha256 changed. Old cert was not expired yet, but it's now replaced with new one. But, it looks like Chrome does not ...
user1209216's user avatar
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The Linux kernel (at least before using XArrays as far as I'm aware, which to my knowledge are wrappers around Radix Trees anyway) uses radix trees in its address_space structs which every file has. ...
Mike's user avatar
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I am investigating the memory impact of containerising two processes that depend on the same shared object. My main question is whether the shared object will be loaded in memory twice or not. This ...
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4 answers
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I'm setting up a Linux system in KVM (QEMU) to test the effect of adding a writeback LVM cache on a fast disk in front of a logical volume that resides on a set of very slow disks (a RAID1 LV). This ...
Kusalananda's user avatar
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I have an existing LVM volume group with a 10 TB logical volume mounted as an ext4 system which is actively in use. Is it safe to run the command lvconvert --type cache --cachepool storage/lvmcache-...
Mikko Rantalainen's user avatar
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On an Apache server of my own, logging requests to files has been enabled using a custom Apache module. The log files can reach several GB at the end of the day. Using Nagios I have noticed memory ...
tigrou's user avatar
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I am trying to understand the CPU cache performance in a single producer single consumer queue algorithm, but cannot pinpoint the cause of performance degradation in some cases. The following ...
xealits's user avatar
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Because there is a situation in my project where files cannot be saved to disk after being written, these two scripts have been added in the background. Will they have any impact on system performance?...
Vimer's user avatar
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I am trying to cache CIFS share files on a ramdisk with cachefilesd, however cachefilesd requires the cache directory filesystem to support user_xattr. tmpfs does not by default. Is there any way to ...
kataba's user avatar
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1 answer
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I'm currently working on the POD supercomputer at UT Austin. Tech support for the supercomputer couldn't help me. There's a specific version of Python (3.9) I want to use in my Anaconda environment, ...
himinam's user avatar
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2 answers
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The Linux kernel implements the page cache to accelerate I/O operations. It would be helpful to be able to turn off and on the page cache for research and testing. How can the Linux page cache be ...
Neverland's user avatar
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0 answers
519 views

It seems like there are no dns clients(????).... but it's impossibile, it's just don't know how to find it. $ sudo lsof -i :53 -S does not return anything. systemctl restart nscd #or systemd-resolve -...
Allexj's user avatar
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I have a linux media server that I use mainly with plex and Serviio(dlna server). I have a t400 4gb gpu (transcoding), 16GB ddr4 ram and an i7-6700 cpu. Now, I have 3 SSDs: 1TB for movies, 250GB for ...
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I have a system which is a USB gadget. It exposes one of its partitions over USB using functionfs to allow the host to provide update files: set -e CONFIGFS_ROOT=/dev/gadget CONFIGFS_DEV=$...
Toby Speight's user avatar
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I am working on an embedded Linux system, where kernel is 5.10.24, and UBIFS on MTD is used. The testing team had a test, which writes a disk file (open, write, close in order), then powers system off....
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The name cache on FreeBSD is responsible for caching file names and their vnodes. It also provides a special database for hashing the contents of large directories. I would like to know how to empty ...
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1 answer
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(Moved from Stack Overflow.) I have a simple backup process that copies a bunch of files to a USB flash drive. I want to verify that copying was successful by re-reading the flash drive and comparing ...
Dale's user avatar
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1 answer
10k views

In my lubuntu 18.04 distribution I have installed google-chrome version 114. By a bash script, at every boots, Chrome is launched and connects to a specific URL. The URL is always the same, but ...
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4 votes
4 answers
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I'm hunting for a way to utilise a slow 500GB magnetic HDD alongside a fast 500GB SSD. I'd like to end up with a reasonable fraction of the two combined [hopefully > 800GB] in terms of capacity, ...
Philip Couling's user avatar
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We have a pretty mixed environment in terms of operating systems. Suse 12/15, Oracle Linux 6/7/8, Redhat 6/7/8 and a few others. We've been using Active Directory authentication for some time. For ...
tmorais's user avatar
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2 answers
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I am working on scripting a way to flush DNS cache on different Linux distros.  I want to support doing this with Ubuntu-Server, Ubuntu Desktop, CentOS 8 Desktop, and CentOS 7 Server (no GUI). I have ...
Dave's user avatar
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0 votes
1 answer
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I have a smb mount on my linux server, but occasionally it loses connection, interrupting the software using the mounted directory. Is there a way to cache the smb mount on local disk?
hobyte's user avatar
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1 answer
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This is a follow-up question to dentry/inode caching on multi-cpu machines / memory allocator configuration, but here I try to put the question differently. My problem is that I have a dual socket ...
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0 answers
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While doing performance benchmarking on CPLEX, I ran across a strange issue. The details are posted in a blog: https://community.ibm.com/community/user/ai-datascience/blogs/xavier-nodet1/2021/07/08/...
LaszloLadanyi's user avatar
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0 answers
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I am trying to get the L3 cache miss rate when I try to use perf. The following is the command I run: perf stat -e instructions,LLC-load-misses,LLC-loads ./program <arg1> <arg2> <arg3&...
darkdante's user avatar
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1 vote
1 answer
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System: embedded, arm64 (4xCortexA53), 2GB LPDDR3, eMMC memory, Linux, kernel 5.4.17. I am experiencing issues with random system crash, that in normal operation will happen every 2 days to every &...
OskarM's user avatar
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0 votes
1 answer
165 views

I've read that cygserver can improve performance in some circumstances but I'm not really clear on how - or on how to know whether it's applicable to our use case. Can anyone provide any insights?
Slbox's user avatar
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1 vote
0 answers
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Various answers on various StackExchange sites cover parts of this topic, but I did not see an exact match for this scenario. How can you identify every mounted standard filesystem, and traverse all ...
mhcomputing's user avatar
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0 votes
0 answers
5k views

In our production environment we are running drop cache command echo 3 > /proc/sys/vm/drop_caches to free the RAM. But also what I found is dropping caches is not a good practice and also it won't ...
Swastik's user avatar
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0 votes
1 answer
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In a VM of 16GB RAM, we are running rsync as a cron job(for every 10 minutes) on our production to sync GBs of folder from AWS EFS to local storage. After few days of running we found that the VM is ...
Swastik's user avatar
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1 vote
1 answer
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Let's say I copy a file using cp and the proccess returns immedietly because the file was written to cache. Then I leave the PC alone for 1 hour. Nothing special running on it. Is the cache flushed ...
zomega's user avatar
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-1 votes
1 answer
52 views

I notice that when I compile a custom build of a packaged program stored in /usr/bin eg /usr/bin/emacs, which emacs shows the already existing executable at /usr/bin/emacs instead /usr/local/bin/emacs,...
vfclists's user avatar
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Like I will use google chrome whenever I use linux (most probably) But I don't want it to auto start when ever I open it. I could open it manually, but I have HDD so it is pain to load for the first ...
Afroz Alam's user avatar
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0 votes
2 answers
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I would want to know if it is possible to search packages in Fedora (using dnf) without it having to sync anything previously. I've read Fedora wiki about rpm, but I don't think I understand properly ...
PolGZ's user avatar
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1 vote
1 answer
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After reading this link: How do you empty the buffers and cache on a Linux system?, I know that there are some commands that can help us to empty the buffers and cache of the OS. But I'm not sure if ...
Yves's user avatar
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2 votes
1 answer
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I'm using a system with multiple storage devices with different write throughput. As explained in question Why were "USB-stick stall" problems reported in 2013? Why wasn't this problem ...
Mikko Rantalainen's user avatar
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1 vote
1 answer
422 views

I was under the impression that dropping the cache via the vm.drop_caches sysctl would drop all caches, but when I freeze a filesystem and drop the page cache, I can still read the directory: # fgrep '...
forest's user avatar
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