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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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`yum clean all` differs regarding handling disabled repositories

I'm porting some old build scripts from CentOS 7 to Rocky 8. I've noticed that the following command cleans all repository caches on Rocky 8, as opposed to just the caches of the one enabled ...
liori's user avatar
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7 votes
4 answers
637 views

Simulate slow disks in KVM to see effect of LVM cache in test setup

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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0 answers
21 views

how to manage size of /home .cache and .local folders

running RHEL 8.10 x86-64 on a server with many users, /home is on a separate partition, and all user accounts as defined in /etc/passwd have their account under /home but there is a separate /data ...
ron's user avatar
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1 vote
1 answer
176 views

Is it safe to add LVM cache device to existing LVM volume group while filesystem is mounted?

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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2 answers
51 views

Is it possible to get a higher memory buff/cache usage after writing a lot of data to the disk?

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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2 votes
0 answers
45 views

A simple memcpy loop with stride of 8-16-32 Bytes, no L1 cache misses, what stalls backend cycles?

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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0 votes
1 answer
56 views

What are the issues with timing sync and clearing cache?

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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1 vote
1 answer
184 views

Any way to enable user_xattr on tmpfs?

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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0 votes
1 answer
172 views

How do I clear the cache without restarting my terminal?

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
0 votes
2 answers
1k views

How to disable the Linux page cache

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
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Can't flush dns in kali linux in Virtualbox. It seems like neither of these are my dns client: systemd-resolve, resolvectl, nscd, dnsmasq

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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0 votes
1 answer
956 views

It possible use SSD as cache?

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 ...
vincenzogianfelice's user avatar
1 vote
0 answers
49 views

Can I invalidate the buffer cache of a block device?

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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1 answer
124 views

Question on tuning file system cache in Linux UBIFS on MTD

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....
wangt13's user avatar
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0 votes
1 answer
63 views

How to empty name cache on FreeBSD?

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 ...
Mateusz Piotrowski's user avatar
1 vote
1 answer
147 views

How to drop the contents of the block cache of a partition/drive in Linux?

(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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0 votes
0 answers
17 views

Flashing a bootloader without the use of sync doesn't work [duplicate]

So some background I was scripting building an SD Card Image for the Anbernic RG350M device. This involves flashing a boot loader to the image. See below. dd if="./select_kernel/squashfs-root/...
AeroMaxx's user avatar
  • 199
0 votes
0 answers
61 views

Is it possible to implement kvm/qemu VM guests and host connected through shared memory to collect and cache data between them

The configuration: host: Ubuntu:20.04 OS guest: Ubuntu20.04 OS The two files use the 9p file system for interworking. The mount command is as follows, mount -t 9p -o trans=virtio tmp_shared /mnt -...
Betty's user avatar
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0 answers
80 views

Selectively exclude paths or filesystems from Linux disk read cache

The Linux kernel uses unused RAM for disk read caching. This is generally a good idea. But is there a mechanism to selectively exclude certain paths or mounted filesystems from this cache? ZFS for ...
1N4001's user avatar
  • 379
1 vote
1 answer
5k views

How to clear all cache data of google-chrome by commands executed by a bash script?

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 ...
User051209's user avatar
3 votes
4 answers
2k views

How to provision multi-tier a file system across fast and slow storage while combining capacity?

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
0 votes
0 answers
1k views

Do we really need NSCD service running? What are the pros and cons?

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
  • 11
0 votes
2 answers
11k views

How do I clear the dns cache on CentOS 7 and CentOS 8?

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
  • 621
0 votes
1 answer
610 views

cache smb mount on local hard drive

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
  • 113
1 vote
1 answer
400 views

NUMA aware caching on linux

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 ...
LaszloLadanyi's user avatar
1 vote
0 answers
137 views

dentry/inode caching on multi-cpu machines / memory allocator configuration

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
0 votes
0 answers
1k views

Unable to use perf to find L3 Cache miss rate

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
1 vote
1 answer
253 views

DDR memory errors or page cache corruption?

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
  • 11
0 votes
1 answer
92 views

Does cygserver improve Cygwin performance? If so, with what tasks?

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
  • 271
1 vote
0 answers
60 views

Clean ways to prime the kernel inode cache after boot?

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
0 votes
0 answers
2k views

linux drop_cache using "echo 3 > /proc/sys/vm/drop_caches" not working as expected

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
  • 103
0 votes
1 answer
1k views

Is rsync really a culprit for causing low memory on our VM?

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
  • 103
1 vote
1 answer
56 views

Is file cache flushed automatically after time?

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
  • 972
-1 votes
1 answer
39 views

Does logging into a shell session build a cache of executables on the path which never gets updated? [duplicate]

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
  • 7,619
1 vote
1 answer
519 views

Is it possible to load up a binary into ram, without executing it?

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
0 votes
2 answers
196 views

Search [not install] without syncthing on Fedora

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
  • 93
1 vote
1 answer
2k views

Is it safe to clear the buffers and cache on a linux server

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
  • 3,331
1 vote
1 answer
798 views

How to change the default BDI `max_ratio` and/or `min_ratio` for all devices?

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
1 vote
1 answer
303 views

Flushing the filesystem cache with a frozen filesystem

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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6 votes
1 answer
2k views

Why is my system using swap when RAM fills up with cache?

I'm running openSUSE TW, 32 GiB RAM, 64 GiB swap (SSD). Swap usage is zero up until the point when RAM gets entirely filled up with cache. I'm using htop to monitor it. Cache is marked yellow/orange. ...
TypicalHog's user avatar
1 vote
1 answer
3k views

What exactly is being cached when opening/querying a SQLite database

I was asked to improve existing code to query SQLite databases. The original code made a lot of separate calls to the database and filtered the results in Python. Instead, I opted to re-write the ...
Bram Vanroy's user avatar
0 votes
0 answers
389 views

USB drive error SCSI cache

just recognized an unknown error, as i checked my actual log with journalctl -f. When i unmounted my Backup-USB-disk with unmount /path/to/disk and then pulled the cable out, a short noise occured ...
lukeflo's user avatar
  • 131
0 votes
1 answer
2k views

Linux Cache cannot be cleared completely, it fills the entire RAM after some days

I use a laptop for work and therefore I only do a suspend to RAM rather than shutdown everyday. so I do not have to start each application again every day. after some days of "run time" I ...
StefanKaerst's user avatar
5 votes
1 answer
10k views

How to flush routing cache in Linux?

There is an Oracle Linux 7 system with Unbreakable kernel 5.4.17-2136.304.4.1.el7uek.x86_64 (which is very recent for the RHEL7-like system, which usually uses 3.10-based kernel). Network interfaces ...
Nikita Kipriyanov's user avatar
1 vote
1 answer
85 views

Do linux processes actually separate cache?

It seems like every time someone complains about how a lot of memory is being used, all of the responses claim that it is just cache, it isn't harmful, it will be reallocated when needed, etc, even ...
Teipekpohkl's user avatar
-1 votes
1 answer
2k views

what is the different between Buffer Cache that displayed from free command VS the available memory [closed]

we have 463 RHEL 7.6 machines in the cluster most of then are HDFS machines ( datanode ) from free -g command we can that usually buff/cache is around 30-50 when total memory is 256G as I know - a ...
yael's user avatar
  • 13.4k
0 votes
1 answer
50 views

Using excess video memory for disk caching?

On newer Ryzen 5000-based laptops, the integrated graphics controller always gets at least 1GB of shared video memory. In the BIOS settings, 1GB is the minimum. For people who don't need 1GB for video ...
rubunu's user avatar
  • 1
0 votes
1 answer
904 views

Disabling any and all forms of write buffering and write caching

I have recently discovered that the cause of my systems' instability is that Linux is buffering writes, and it is doing so for all devices of any form, and it is not caring how much destruction it is ...
AshleighTheCutie's user avatar
1 vote
0 answers
627 views

Security concerns for gpg-agent caching the passphrase?

https://www.gnu.org/software/emacs/manual/html_node/pgg/Caching-passphrase.html When using GnuPG (gpg) as the PGP scheme, we recommend using a program called gpg-agent for entering and caching ...
midnite's user avatar
  • 443
1 vote
1 answer
867 views

How to set GPG cache ttl in a shell script?

How to set gpg-agent --no-allow-external-cache --default-cache-ttl 10 --max-cache-ttl 20 in a shell script? After I issue the command, it gives gpg-agent[4869]: gpg-agent running and available but ...
midnite's user avatar
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