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25
votes
3answers
2k views

Does grep use a cache to speed up the searches?

I have noticed that subsequent runs of grep on the same query (and also a different query, but on the same file) are much faster than the first run (the effect is easily noticeable when searching ...
3
votes
3answers
76 views

Speed up copying 1000000 small files

I have 1000000 4-20 kb files in a dir. I need to copy that dir. But it seems I have to do a seek for each files so this takes quite a while. Is there a way in which I can speed this up? I am ...
3
votes
3answers
20k 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 ...
5
votes
2answers
450 views

what does it mean by cold cache and warm cache concept?

I read a paper and it used terms “cold cache” and “warm cache”. What does it mean by cold cache and warm cache concept? I visit this but I need something more.
0
votes
0answers
41 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 IO at the beginning ...
15
votes
4answers
13k views

Where are stored the Youtube videos cache in Google Chrome?

Google Chrome used to store YouTube videos in /tmp, but not for the last two versions. Nor could I find those files in ~/.cache/google-chrome. Googling for this query produces Windows-specific ...
0
votes
1answer
33 views

Is there a way to prevent SWAP from collecting cached data?

Here is the following info: Do I need more swap? No, disk caching only borrows the ram that applications don't currently want. It will not use swap. If applications want more memory, they ...
0
votes
1answer
83 views

How to find the page size, associativity, and TLB size and number of entries?

Under an Ubuntu system, are there commands for looking up: the page size, n in n-way cache associativity, TLB cache's size and number of entries?
2
votes
3answers
724 views

delayed write in operating file system

I read in some papers about NFS and Sprite that a system can use delayed writes when a client writes something to the server. I would like to know what is the purpose of this technique?
0
votes
1answer
33 views

When speaking about cache size of a CPU, we only need the size of the cache at the furthest level [closed]

When speaking about cache size of a CPU, do we only need to know the size of the cache at the furthest level (such as at level 3, when the cache hierachy is 3-level)? Instead of the sum of all the ...
1
vote
2answers
203 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 ...
1
vote
1answer
57 views

Web server seems to keep serving old images, issue with Apache & VirtualBox?

I'm asking this here because I'm pretty sure it's a Linux issue. I'm running Apache server locally on Ubuntu Server 12.10, which runs inside a virtual machine (VirtualBox) on Windows 7. The "www" ...
0
votes
1answer
25 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.
0
votes
2answers
259 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?
3
votes
1answer
171 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 ...
16
votes
7answers
4k views

Linux equivalent to ReadyBoost?

Is there a kernel module or some other patch or something similar to Windows' ReadyBoost? Basically I'm looking for something that allows disk reads to be cached on a Flash drive.
1
vote
0answers
175 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. ...
4
votes
2answers
300 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 ...
2
votes
3answers
3k 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
4
votes
0answers
210 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 ...
18
votes
4answers
17k 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).
1
vote
1answer
1k views

“sync” before drop_caches,is it 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, drop_cache is a non-destructive ...
2
votes
0answers
33 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
vote
2answers
389 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 : ...
53
votes
2answers
11k views

How do I clear Bash's cache of paths to executables?

When I execute a program without specifying the full path to the executable, and Bash must search the directories in $PATH to find the binary, it seems that Bash remembers the path in some sort of ...
3
votes
0answers
368 views

Linux: Write cache tuning

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
0answers
44 views

looking for name of a userspace tool for disk/network caching? [closed]

I remember seeing a blog post a month back that used a tool in the command which acted like a user space caching tool to buffer/cache reads and writes in RAM to overcome disk or network contention. I ...
1
vote
1answer
65 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 ...
0
votes
1answer
283 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 ...
9
votes
1answer
2k 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?
1
vote
3answers
1k 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
2answers
72 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
votes
1answer
56 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 ...
2
votes
2answers
456 views

mbcache documentation

I want to experiment with mbcache kernel module, but I'm having trouble finding the documentation for it. If I understood correctly, mbcache allows the use of a fast SSD disk to act as a transparent ...
3
votes
2answers
357 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
1answer
250 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 ...
8
votes
5answers
4k 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 ...
-1
votes
2answers
1k 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 ...
4
votes
2answers
356 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
275 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
64 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 ...
5
votes
1answer
508 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
votes
1answer
97 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 ...
7
votes
3answers
477 views

Why does it makes sense to cache swap?

It sounds quite counter-productive to me to cache pages that are swapped out. If you swap pages in, what is the advantage to first cache them in memory, only to have to than move them to the right ...
4
votes
4answers
370 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?
13
votes
2answers
702 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
1answer
364 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. ...
1
vote
1answer
3k 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?
1
vote
1answer
118 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 ...
2
votes
1answer
265 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 ...