The cache tag has no wiki summary.
3
votes
2answers
77 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 ...
7
votes
1answer
113 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 ...
3
votes
1answer
23 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
2answers
86 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
38 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 ...
-2
votes
2answers
440 views
Where can I find a good tutorial for installing bcache? [closed]
I found on the net and it's all too complicated.
http://bcache.evilpiepirate.org/ for example seems like the official page for bache. Yet nothing is found there. How to install? How to set up? ...
4
votes
1answer
71 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
35 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
400 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
187 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
573 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
48 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.
...
0
votes
1answer
54 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
50 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 ...
11
votes
6answers
2k 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
2answers
2k 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 ...
2
votes
1answer
77 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
197 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 ...
3
votes
1answer
258 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 ...
1
vote
0answers
767 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 ...
0
votes
1answer
157 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
2answers
166 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 ...
4
votes
1answer
153 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 ...
3
votes
0answers
224 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 ...
1
vote
1answer
298 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
122 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 ...
0
votes
0answers
277 views
How do I flush local DNS cache on my machine? [closed]
I've found that reloading the nscd service (/etc/init.d/nscd reload) should do this. However, I don't have a nscd file in my /etc/init.d directory, so how do I perform this?
11
votes
2answers
10k 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
2answers
143 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
votes
2answers
367 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 ...
14
votes
4answers
10k views
Google Chrome cache
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 ...
1
vote
2answers
1k 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
2answers
91 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
221 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
601 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
57 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 ...
2
votes
1answer
256 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 ...
1
vote
4answers
1k 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
177 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 ...
5
votes
1answer
283 views
Why doesn't dm-crypt handle write barriers properly?
One of the well-known properties of dm-crypt is that it does not handle write barriers properly and hence it requires turning off on-drive write cache to prevent corruption of filesystems. As far as I ...
0
votes
0answers
93 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
261 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 ...
8
votes
2answers
527 views
lshw and lscpu disagree on caches - which is right?
I am trying to find out specifics about caches (in particular which caches are shared between cores and which are not) and have stumpled onto a inconsistency.
sudo lshw says
*-cache:0
...
5
votes
2answers
4k views
Cleancache vs zram?
I have an old laptop here with only 512 MB of RAM. Since a few kernel releases, I am using zram to convert 256 MB of it to a compressed ramdisk which is then used as swap. This has proved to be very ...
4
votes
3answers
273 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 ...
0
votes
2answers
147 views
Caching bugzilla webpages for offline use
I have a long wifi free journey ahead of me and I would like to continue to productively review bugs even without the ability to change them.
Is there an easy way to cache all the pages generated ...
11
votes
1answer
990 views
Is disabling barriers for ext4 safe on a laptop with battery?
The manual page says about the barrier option for ext4:
Write barriers enforce proper on-disk ordering of journal commits, making volatile disk write caches safe to use, at some performance ...
4
votes
1answer
422 views
Drop a specific file from the Linux filesystem cache?
I know I can drop everything from the Linux filesystem cache, but is there a way to drop just one specific file? Or prevent a file from being cached? Or tell a process not to cache any files it ...
2
votes
1answer
406 views
What is the buffers column in the output from free?
These questions briefly list the format of the free command, noting that buffers is kernel memory that must be written out to disk and cache is file data that does not need to be written disk.
On my ...
2
votes
2answers
225 views
`free`: output format
I use free to get the amount of free space on some of my servers. Its output is something like:
$ free -m
total used free shared buffers cached
Mem: 374 ...
