The tag has no wiki summary.

learn more… | top users | synonyms

1
vote
0answers
18 views

Ubuntu: Restore not printed document from browser cache

I was at work today faced with a situation where I have to prove that I did not make a mistake. Without going into detail, yesterday I generated an important document which was to be printed. For ...
1
vote
0answers
25 views

What is being cached?

I have an embedded system with a low amount of memory. The system has allocation issues. Maybe due to fragmentation: Memory allocation issue on NOMMU? The platform is a NOMMU platform and so I suspect ...
0
votes
1answer
34 views

What dev folder allows you tell the OS to cache something?

Someone told me that there is a sub folder off of dev that basically allows you to tell the OS to keep the contents of that folder cached in RAM. So if I put some files & directories in ...
2
votes
1answer
58 views

Spawn multiple dirty page flusher threads per device

In earlier 2.6.X kernels, pdflush was used and it would spawn more pdflush threads if all current pdflush threads were busy for a second (read from The Linux Page Cache and pdflush). Since the ...
2
votes
1answer
59 views

Fix “Route hash chain too long” without restart

On our production server (ubuntu 12.04, 3.2.0-63 kernel) routing cache reached its capacity. Modifying rhash_entries is out of the question, since it is a kernel boot param, and we can not restart the ...
2
votes
2answers
25 views

How should I restore /var/cache?

I just restored my Raspberry Pi server from an rsync image. During the backup, I had excluded /var/cache/*, thinking that this would restore an empty directory. This worked, but when I rebooted, a ...
3
votes
3answers
2k views

/proc/cpuinfo “cache” category: L1, L2 or total?

When I look in /proc/cpuinfo, one of the lines tells me I have 6144 KB of cache. Is this L1 cache, L2 cache, or the sum of both of them? In any case, how do I find out how much L1 and L2 cache my ...
16
votes
1answer
11k 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?
3
votes
0answers
34 views

Figuring out physical cache layout in FreeBSD

I'm trying to figure out they physical cache layout of my CPU in FreeBSD 10. I see the following from sysctl kern.sched.topology_spec kern.sched.topology_spec: <groups> <group level="1" ...
3
votes
1answer
61 views

Artificially prime buffer cache?

Is it beneficial to artificially prime the buffer cache when dealing with larger files? Here's a scenario: A large file needs to be processed, line by line. Conceptually, it is easy to parallelize ...
1
vote
0answers
10 views

Can not analyze output from Squid and varnish

I'm using one Squid server between tow cache server. I get from headers following information: X-Cache MISS, HIT from cache-zz X-Cache-Age 515 X-Cache-Control public, max-age=3600 X-Cache-Lookup HIT ...
2
votes
3answers
6k 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.
0
votes
0answers
16 views

how to find where buffers/cache are and how to clean them up? [duplicate]

I want to create 20gb ram disk for ANSYS to work in yet on free -g I see: And personally I have not created any ram drives yet. So I wonder how to maximize avaliable ram: how to locate what is using ...
2
votes
0answers
48 views

Reduce cache size of flash storage devices

For various benefits Linux uses a memory cache for writes to removable stogare devices like memory sticks. This cache seems to be quite large on my system, which leads to some annoying behavior. For ...
2
votes
0answers
14 views

In meminfo, sometimes Mapped more than Cached

In /proc/meminfo, AFAIK Cached >= Mapped But after /proc/sys/vm/drop_caches, it goes to Cached < Mapped Cached: 66132 kB Mapped: 67792 kB /proc/meminfo contents ...
1
vote
1answer
2k 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 ...
3
votes
1answer
444 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 ...
4
votes
3answers
31k 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 ...
0
votes
0answers
37 views

Can't configure NGINX to cache images

I have been trying to cache images that are stored in nginx server, I am quite new here and to nginx I have installed it and configure it with php5-fpm, I have been reading many tutorial regarding ...
1
vote
1answer
64 views

Random application crashes in Linux

Sometimes after booting my computer, some applications fail to start: they crash. They're usually the largest ones, such as firefox, thunderbird or virtualbox. Rebooting or cleaning the cache usually ...
0
votes
1answer
60 views

should I reduce /dev/shm size?

I have a server wity 8 GB RAM Mem: Total 8031464 Used 5146344 Free 2885120 If I execute # df it always returns this tmpfs 4015732 0 4015732 0% /dev/shm What does it ...
3
votes
0answers
513 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
4answers
6k 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?
7
votes
5answers
14k views

DNS queries not using nscd for caching

I'm trying to use nscd (Nameservices Cache Daemon) to cache DNS locally so I can stop using Bind to do it. I've gotten it started and ntpd seems to attempt to use it. But everything else for hosts ...
3
votes
2answers
327 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 ...
1
vote
1answer
160 views

Clear Memory Cache on Amazon EC2

In our project we have a few tests which run for about 3-4 hours continuously. In due course, the tests fail as they couldn't find enough memory. On googling, I found that running the following ...
5
votes
1answer
176 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 ...
26
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
172 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 ...
5
votes
2answers
917 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
97 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
14k 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
52 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
352 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
908 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
83 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
242 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
151 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
33 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
997 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
393 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 ...
17
votes
7answers
5k 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.
2
votes
0answers
287 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
432 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 ...
5
votes
0answers
278 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 ...
19
votes
4answers
21k 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).
2
votes
0answers
41 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
799 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 : ...
68
votes
2answers
14k 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 ...
1
vote
0answers
51 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 ...