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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1answer
72 views

How to print a Bind10 cache dump?

How can you print the current state of the bind10 cache? I searched the bind10 manual and tried to figure it out using bindctl.
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2answers
5k views

Clear file system cache on AIX

I'm using AIX 6.1 and for testing. I want to clear the file system cache. Something similar a this on linux : echo 2 > /proc/sys/vm/drop_caches Is this possible?
4
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2answers
1k views

SSD as a read cache for FREQUENTLY read data

I'm looking for ways to make use of an SSD to speed up my system. In “Linux equivalent to ReadyBoost?” (and the research that triggered for me) I've learned about bcache, dm-cache and EnhanceIO. All ...
3
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0answers
874 views

Route all HTTP traffic through polipo

I've set up polipo on my machine to listen to the default port 8123. To test it, I set the in-memory cache to a ridiculously high 2 GB and downloaded a 50 MB file using wget utilizing the proxy. ...
2
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0answers
76 views

Too large cache causes disks to grind, I/O to drop

This is a followup question to my earlier problem. In short I was experiencing massive I/O drops together with not-so-violent disk grinding, and with help I found out that the big caches were the ...
1
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2answers
2k views

DNSCrypt, Unbound and DNSSEC

I would like to have an encrypted DNS queries + a DNS Cache + Domain Name System Security Extensions (DNSSEC) . I used this bash script to install DNSCrypt and I choosed to use dnscrypt.eu servers : ...
3
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0answers
1k views

Tune write disk cache flushing algorithm

I would like to use the free memory for write cache. Linux does that automatically, but it has some weird flushing algorithm that I would like tuned for my use. I have recently used ddrescue to copy ...
1
vote
1answer
136 views

External Cache not socketed

When I check my CPU Cache with command dmidecode, I get Cache configuration to be Not Socketed. What does that mean? prayag@prayag:~/hacker_/draobkcalb$ sudo dmidecode -t cache # dmidecode 2.11 ...
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2answers
6k views

How to reduce buffers\cache

A monitoring system keeps alerting that my machine is reaching\breaking through it's RAM utilization threshold which is 15 GBs. I've done some reading and understood that the apparent RAM utilization ...
8
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1answer
889 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 ...
1
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2answers
121 views

Configurable DNS cache for Linux

What I need is to configure a Linux machine, so that when user of that machine goes to www.somesite.com he/she is redirected to, say, 127.0.0.1. What is the best way to achieve it?
2
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1answer
97 views

Monitoring file reads for cache warming

After adding more memory to my Linux machine I was tempted to use the cache more agressively. The thing is: I boot up my machine, go to bathroom, come back and log in. It takes like half a minute to ...
132
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1answer
283k views

How do you empty the buffers and cache on a Linux system?

Prior to doing some benchmarking work how would one free up the memory (RAM) that the Linux Kernel is consuming for its buffers and cache?
4
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3answers
1k views

Are there any ways or tools to dump the memory cache and buffer?

As the title, I want to check out what files are loaded in buffer. Just so it's clear, the buffers & cache I'm referring to are what show up when you run the free -m command: $ free -m ...
3
votes
1answer
5k views

Is “sync” before drop_caches necessary?

I have read a lot of docs saying, it is good idea to do a sync before doing echo [1,2,3] > /proc/sys/vm/drop_caches. I am not able to understand why it is needed, since drop_cache is a ...
7
votes
2answers
2k views

Find/ls caching

It seems as though the first time I run find or ls on a directory, it takes a while to work. But, each time thereafter, it is fast, as though a list of the directory's contents has been cached or ...
4
votes
1answer
2k views

How can I tune Ubuntu for running from a flash drive?

I feel like this is a bit of a duplicate of this other question about making caching more aggressive, but I tried a lot of the suggestions there and I just can't figure out why I'm having trouble. My ...
1
vote
1answer
206 views

How to stop CACHE instance from Shell Script

I want to restart CACHE(database that I am using) Instance from shell script. What I did is created a function in the shell script named resatrt_cache. restart_cache() { ccontrol stop instancename ...
9
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1answer
1k views

How to configure Linux to cache file metadata in preference to contents?

I’d like to set the system up to use most RAM for file system metadata caching, but only a reasonably small amount for read/write caching and prefetching files. Ideally I would like to be able to ...
3
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1answer
148 views

Ubuntu filesystem buffers/cache always empty

I have a virtual server with ubuntu 10.04.4 LTS and plesk (preinstalled by hosting company). Now i have seen that the buffers/cache are always empty. Current uptime is 22 days. free and htop shows the ...
3
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1answer
1k views

How to guarantee writes are physically committed before reported completed?

When my system boots, as it probes the external, USB-attached hard drive, I get the message Assuming drive cache: write through in the dmesg output, tagged with the device name of the external drive. ...
18
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1answer
20k views

How can I tell which version of Varnish I'm running?

How can I get the installed Varnish cache version string from the command line?
2
votes
2answers
321 views

Keeping disk caches when hibernating

Is there a way to keep disk caches when hibernating Linux? I understand and agree that dropping them is the best option all-around. But my system is unresponsive after resume and I would like to give ...
8
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2answers
778 views

Linux cache evictions

Looking at how the VFS cache on my Linux machine behaves, I can see that even when effectively idle (crond and most other daemons stopped, interfaces down) the amount of free memory gradually ...
6
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3answers
100k views

How to flush local DNS cache in CentOS

(I am aware that googling this question gives me tons of stuff, but literally none worked) I'm looking for a way to flush the local DNS cache on a Centos 6 system, it is not running any DNS server or ...
4
votes
1answer
1k views

DNS cache for wget

I want wget to use a global DNS cache, not just in memory for the current instance. The wget manual mentions --no-dns-cache Turn off caching of DNS lookups. Normally, Wget remembers the IP ...
3
votes
2answers
693 views

Memory management, bias to swapping

I was having 768 MB RAM. In a general day MySQL was using 100-180 mb of RAM and MySQL was swapping 80-120 mb. I was having 50-60 mb free RAM. So I thought I should upgrade. Then I upgraded my RAM ...
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2answers
562 views

TLB cache flusing when a page is swapped out

I recently heard that Linux simply flushes the TLB cache when the corresponding data in that physical address is swapped out, resulting in underutilization of the TLB. I don't know whether all OSes do ...
3
votes
1answer
965 views

Measure hard-disk read(), write() speed without caching in QNX 6.5

I am working on QNX 6.5 Operating system. QNX 6.5 supports POSIX APIs. I am trying to build an application which is used to evaluate performance of hard-disks. My application will read/write/read ...
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0answers
2k views

How to set up ZFS with ZIL and L2ARC SSD?

I have been considering bcache and flashcache. However my friend suggested me something called ZFS. In fact it says that formating disk with ZFS can actually do the exact same thing without kernel ...
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2answers
2k views

Where can I find a good tutorial for installing bcache? [closed]

Question is updated. Now bcache is part of the standard OS compilation. So it should be easy to install that now. I'll just order some SSD and some big HDD. Where can I found it? I found on the net ...
0
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1answer
522 views

Does linux have something like supercache?

I installed http://www.superspeed.com/desktop/supercache.php for windows and the result is awesome. Every program I run is faster. Basically it uses the memory to cache data. Simple idea. I also use ...
4
votes
4answers
939 views

If I have an SSD and a hard disk in a system, can the SSD act as cache for the hard disk?

Say I have some partitions; one on a SATA drive and one on an SSD. I want to create a "virtual" hybrid disk. Is this possible?
4
votes
1answer
446 views

Limit disk buffer usage in SLES 11SP2 to allow more efficient memory overcommit on esxi host

When running VMs on an ESXi host, you can overcommit the memory. Example: host == 20GB physical RAM The amount of RAM allocated to each VM is VM1 == 10gb VM2 == 10gb VM3 == 10gb VM4 == 10gb The ...
4
votes
3answers
646 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 ...
3
votes
2answers
929 views

iptables routing marked packets from router to PC and routing them back to router

I'm trying to do deep packet inspection on HTTP packets. The purpose of this is to collect HTTP payload data and then create some proxy/cache-independent reports. Following this, the idea is to ...
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
413 views

How to debug/audit which devices cache writes?

I store documents on btrfs partition built upon sparse dm-crypt device located on ext4 main partition on physical harddrive. When kernel panics (and this happens on daily basis on my ASUS P53E with ...
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 ...
3
votes
2answers
592 views

linux disk caching affects access times reported by stat?

On Ubuntu 12.04 I did the following stat a file cat the same file stat the file again cat the file again after 5 min stat the file The access time reported at 3. reflects the point at which 2. was ...
2
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2answers
2k views

Can readahead-services be safely disabled?

I am just going through the service-list of a server (CentOS 5) - the question will probably apply to other RedHat, Fedora, ... versions, too. Note that my servers normally run in runlevel 3 (no GUI ...
3
votes
2answers
188 views

RAID Lag-Behind Burst Write

I would like to setup RAID1 so that a ramdisk in the RAID configuration has occasional synchronisation with a physical disk (that is very battery intensive to run, so I hope to let it spinout). Is ...
2
votes
1answer
989 views

How to cache all internet downloads

I am currently running Ubuntu 12.04. How would I go about caching all downloads? And if Linux does not have this built in, then what are good tools for this? Please note that this isn't a browser ...
3
votes
1answer
1k views

AIX 6.1 JFS2 Oracle files system, not using much files system cache

I am running Oracle database on AIX 6.1, Oracle using JFS2 file systems. Maxperm is set to 90%. This is busy database server, but it is not using the file system cache (less then 2%). The system has ...
3
votes
2answers
92 views

How to get size of data that haven't been written to disk yet?

In some programs percentage of copying large files get to 100% very fast and then I'm waiting much more before it goes next step. It's caused by buffer. How to I see amount of data that are going to ...
1
vote
2answers
2k views

How to bypass youtube's local cache?

Youtube performance here in Brazil has been terrible lately. Checking my browser's activity I can see that my ISP has a local Youtube cache and serves videos in 1.7 MB chunks. Talking to some friends ...
3
votes
4answers
21k views

How to clean up the RAM memory that is being used as cache memory?

My processor is using a big part of my RAM memory as cache and I want to clean it up because of that; will it prejudice something?
2
votes
1answer
298 views

How to utilize extended attributes for image preview?

Is there any file browsers for Linux that cache image previews, just like Windows Explorer cache them to a file named Thumbs.db? As in the latest ext3/4 filesystems, an inode can hold extended ...
0
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0answers
113 views

Real copy to Android device

When i copy files to the Android phone, they are copied to some cache, but they aren't written. I don't like it, because i don't know what is done. I've tried these methods: copying via thunar file ...
2
votes
1answer
597 views

Running a query without the OS cache

I want to emulate a client site who doesn't have much caching because they have so much I/O all the time. I want to run a SQL query on my machine (on my VM to be precise) with the same limitations ...