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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0
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2answers
18 views

How to improve Solaris Server Configuration [on hold]

As a programmer I have limited knowledge of the ins and outs of Hardware configuration. I've been tasked with assisting in server tuning. I understand tuning a server for peek performance varies per ...
6
votes
1answer
248 views

Limit the inode cache used by a command

I want to run a task with limits on the kernel objects that they will indirectly trigger. Note that this is not about the memory, threads, etc. used by the application, but about memory used by the ...
5
votes
1answer
17k views

Is no caching mode page a serious error?

My server log displays the following error messages in RED: kernel: sda: sda1 sda2 kernel: sd 0:1:0:0: [sda] No Caching mode page found kernel: sd 0:1:0:0: [sda] Assuming drive cache: write through ...
0
votes
1answer
31 views

Vim saved file not updating on webpage

I am attempting to update an HTML file on my server, but when I do so it doesn't appear to be updating, but rather, serves an old copy instead. I went through the usual process of pressing :w and ...
0
votes
0answers
12 views

stop dm-cache from caching temporarily

I am want to benchmark my system(Centos) IOPS with dm-cache and without dm-cache.I have taken benchmark result for my system dm-cache .Now I want dm-cache to stop temporary so that I can take ...
2
votes
3answers
2k views

Increasing the size limit for /var/cache/apt/archives

I have 2 systems running Debian at home and I am trying to minimize the bandwidth use while upgrading the packages. How can I increase the size limit of the cache, so that I could just copy the ...
1
vote
1answer
8 views

Error while installing Bcache on centOS

I am trying to setup Bcache on my existing system(Its risky,but we are not worried about losing any data ) . So my make and make install works proper but when I run the command make-bcache i receive ...
0
votes
1answer
30 views

device-mapper: reload ioctl on cache1 failed: Device or resource busy

When I run the below command while setting up dm-cache on my CentOS system, I receive the error: device-mapper: reload ioctl on cache1 failed: Device or resource busy Command failed Command is: ...
5
votes
2answers
165 views

How to enable package caching in dnf?

I started using fedora 22 and started learning dnf only to find out about two annoying facts: Almost every time I install or upgrade anything it has to rebuild the whole repository metadata cache ...
1
vote
0answers
10 views

Which is the correct dm-cache version

I am trying to install dm-cache on my CentOS machine. Which dm-cache version should I use. I read on wikipedia as below: Another dm-cache project with similar goals was announced by Eric Van ...
0
votes
0answers
29 views

device-mapper error while setup of dm-cache

I am trying to setup dmcache using the tutorial https://wiki.mikejung.biz/Dmcache When I run the command `dmsetup create home-cached --table '0 976771120 cache /dev/mapper/ssd-metadata ...
3
votes
2answers
60 views

Defer *all* disk writes, keep them in memory

How to temporarily stop synchronizing of dirty data with disk, instead just keeping it in memory. Clarification: I want to sync it later.
8
votes
1answer
881 views

Cleanup of temporary file ~/.cache/duplicity/temp failed

Often when I run Duplicity I see an error message like this at the end of the run: Cleanup of temporary file ...
0
votes
1answer
37 views

How to deactivate linux page/disk cache?

I would like to turn off the disk / storage cache on Raspbian. I have done a serie of benchmarks on the microSD (http://jgp.net/microsd-card-performance-raspberry-pi/) but some people recommended I do ...
1
vote
0answers
45 views

Squid takes a long time to get a response for HTTP requests, never hit neighbor cache [migrated]

I am trying to install Squid in a sibling model by following these instructions. But when the client executes HTTP request it takes a long time to get response from the server. System model: ...
0
votes
1answer
25 views

ncmpcpp is damaged after experienced a crash

My problem appeared with ncmpcpp the console music player. I've used ncmpcpp to open a .pls file from the Browser window and it crashed perhaps due to encoding problems. Since then, Every time I ...
20
votes
6answers
9k views

How to cache or otherwise speed up `du` summaries?

We have a large file system on which a full du (disk usage) summary takes over two minutes. I'd like to find a way to speed up a disk usage summary for arbitrary directories on that file system. For ...
40
votes
5answers
47k views

Can I safely remove /var/cache?

I am running out of disk space and noted that I have a large /var/cache directory. Can I safely remove this? (using Arch Linux, BTW).
3
votes
0answers
90 views

How to interpret perf -e cache-misses:pp?

I find the behavior of perf top -e cache-misses:pp -p <my_pid> quite confusing. I own an Intel i5-3230M, running kernel 4.4.5 64 bit. If I just run that commmand, I get basically no samples ...
0
votes
1answer
73 views

How can I clear my cache?

I'm running a live CD linux distro and I'm getting out of memory exceptions. >java -version #Java HotSpot(TM) 64-Bit Server VM warning: INFO: os::commit_memory(0x0000000646e00000, 264241152, 0) ...
1
vote
1answer
54 views

Linux Gateway as Download Accelerator like IPCop's

We're running dnsmasq on a linux box inside our network for DHCP and DNS. I would like to add a download accelerator like IPCop's (http://blockouttraffic.de/ua_index.php) but without having IPCop as ...
0
votes
1answer
29 views

-/+ buffers/cache & Swap

When should the usage of swap get started? or How do I know that my swap is being used? At least some times if not always, considering the default swappiness of 60 Also, why does free offer to omit ...
0
votes
1answer
29 views

How does the diff command handle caching?

I became curious when I was diffing two large (>326MB) files, and noticed that the second run took much less time than the first. This was frustrating, since I was trying to time the second run, to ...
1
vote
0answers
35 views

bcache not working as expected with ramdisk as cache device

I was trying out bcache but i don't have an SSD so wanted to use free memory as a substitute. As ramdisk is listed in /proc/devices as block device i assumed this would work OK but with below simple ...
4
votes
3answers
645 views

Does sysctl kern.bufcachepercent not work in OpenBSD 5.2 above 1.7GB?

I run OpenBSD/amd64 5.2 on a system with 12GB of RAM, and I want to use about 6GB to 8GB for filesystem caching. By default, 5.2 amd64 comes with sysctl kern.bufcachepercent set to 20 (20%); I've ...
11
votes
3answers
29k views

How to read the local DNS cache contents?

I know that on Windows I can issue ipconfig /displaydns and I see the local DNS's cache content. How can I list the DNS's cache content in Linux? I would like to get as much as cross-distro solution ...
0
votes
0answers
19 views

Is the iSCSI block device having client side-read cache (if yes how to disable)?

I have a remote block device with the test ext4 filesystem image. On the iSCSI initiator side, I have this device detected as let's say /dev/sdb. I am not mounting this filesystem but instead I use ...
1
vote
1answer
49 views

Using terminal to reset icon cache - which method?

I've been trying to find out how to reset the icon cache on my MacBook, and two methods seem to always be suggested. However, the two approaches differ slightly in the third line. Method 1 sudo find ...
0
votes
0answers
41 views

SSD + HDD performance from power on

I'm planing to buy a new laptop with a 128GB SSD and a 1TB HDD. And I would like to have reliability, performance and storage space from power up and during the whole runing time. During the running ...
3
votes
0answers
62 views

How to cache block devices (for device mapper)?

problem / observed effect It seems that the page cache ignores block devices which are not opened. And worse: Reads from device mapper (DM) devices which use a cached device are not cached at all ...
5
votes
4answers
699 views

Does bash have a built in caching command available (sort of like mktemp or sponge)?

I'm using the amazon ec2 command line tools, and the ec2-describe-instances tool is a little painful because of the 2-5 seconds it requires to make the request and display the output. I'm looking ...
4
votes
0answers
106 views

LVM cache and TRIM

I have set up LVM to cache a logical volume (located on an HDD) on a partition of an SSD (in writeback mode if this matters). As far as I can tell, this works correctly and the cache uses all ...
1
vote
1answer
587 views

flashcache tuning

I installed flashcache version 3.1.1 and created a write-back cache. The performance is good as long as the percentage of dirty blocks is not too high. My application does heavy I/O at the ...
13
votes
2answers
1k views

Why does Linux purge the memory cache when it is nearly full?

Here's what the memory graph looks like on a VPS running CentOS with 512MB of RAM and nginx/php-fpm/mysqld serving (mostly static) content to a couple thousand visitors per day. (those are days on ...
7
votes
1answer
991 views

How to use an SSD for caching, so my hard disks can spin down?

I've got a file server with a bunch of disks running together in a BTRFS pool and want to add an SSD for caching. I'm not mainly after speeding up things, but want to catch the regular small accesses ...
5
votes
0answers
164 views

Why are slab objects not reclaimed automatically

Everyday after a full system backup, various programs are failing with read errors until I run echo 2 > /proc/sys/vm/drop_caches to free reclaimable slab objects. For example, here's the output of ...
1
vote
0answers
42 views

One SSD cache for two partitions on two separate disks?

I have two hard drives: one for my operating system and the other for other data. I recently bought an SSD drive that I would like to use an LVM cache for those two devices. The problem is that I ...
8
votes
2answers
55k views

How to clear memory cache in Linux

Is there any command that by using I can clean the cache in RHEL? I used this command: sync; echo 3 > /proc/sys/vm/drop_caches but it didn't work.
1
vote
2answers
60 views

how does o_sync trigger pdflush?

When I write using o_sync, the write call returns once the data has been written to the disk. But how does o_sync force Linux to write the data to disk? Normally you would have to wait a maximum of ...
1
vote
0answers
152 views

OpenLDAP as a Proxy cache only, no local database

I am trying to get a local LDAP proxy cache running. The idea is this: Currently a computer (A) is sending all ldap requests to a remote ldap server (L) Instead of that, there should be a proxy ...
0
votes
0answers
26 views

SSD as write target during reads

I have a real-time application which always writes data to a RAID 10 HDD configuration in a sequential manner at around ~50 MB/s. It uses mmap and writing should never be blocked due to waiting I/O. ...
0
votes
1answer
138 views

how to increase cache memory in centos

I have been facing a insuffient space in "/var/cache/yum" directory. due to this my gui of centos crashes.i want to increase the size of cache directory. also want to know the actual size of cache ...
2
votes
0answers
26 views

Which subsystem caches file reads?

I am trying to understand how exactly file reads are served from Page Cache. This will be useful when I will be implementing my own filesystem in the kernel. Is file content cached by VFS or ...
1
vote
1answer
94 views

Linux top -n 1 Command doesn't get update

I'm calling the Linux top -n 1 -b command from a Qt application to get the free CPU percentage. This application calls this command every 3 seconds, but the CPU usage seems to be updated only the ...
3
votes
1answer
189 views

How to run free command by crontab

I want to run this command: free && sync && echo 3 > /proc/sys/vm/drop_caches && free -m by cron. That way I can free my RAM and cache in an Ubuntu system. I'm using ...
1
vote
1answer
38 views

Reset Bash's memory used for auto-complete

After renaming a file to a similar name, I noticed TAB was still completing the old filename (if it matched the letters so far) and not showing the new one. No matter how many letters I typed, it ...
2
votes
1answer
29 views

Is partition created by dd (and cached) instantly available for writing

I'm creating a partition (from backup) with dd and need to know if there is a need of some sort of sync/timeout before I can access it. As I know data may be cached in dirty pages. But what if I ...
0
votes
0answers
53 views

How to configure some proxy like Squid to download specific URL only once?

I have read article about Windows 10 spying my activity and blocked all mentioned addresses on my router's firewall. This included addresses az361816.vo.msecnd.net and az512334.vo.msecnd.net ...
1
vote
0answers
26 views

what is left inside the cache even after clearing the page cache data?

I was trying to clear the cache using echo 3 > /proc/sys/vm/drop_caches Even after performing the above operation there remain some space inside the cache? When I check with free -m around it ...
1
vote
1answer
281 views

Using readahead in Debian Jessie

The article BootProcessSpeedup on the Debian Wiki lists a tip to speed up boot time. It says to install readahead and then #touch /etc/readahead/profile-once. It seems like an outdated article, ...