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3
votes
2answers
436 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 ...
73
votes
3answers
15k 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 ...
27
votes
1answer
23k 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
votes
2answers
486 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 ...
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.
7
votes
2answers
5k 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 ...
1
vote
4answers
7k 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?
1
vote
2answers
256 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 ...
26
votes
3answers
3k 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
8k 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.
7
votes
2answers
1k views

How to time grep commands accurately?

I want to compare the speed of these two commands: grep pattern1 files* grep pattern2 files* Unfortunately, the first grep reads much of files* into memory buffers, so the second grep runs ...
7
votes
5answers
15k 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 ...
4
votes
4answers
492 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?
3
votes
2answers
348 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 ...
3
votes
1answer
2k 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
1answer
162 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 ...
0
votes
1answer
37 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 ...
0
votes
1answer
99 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 ...
0
votes
1answer
371 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 ...