Linked Questions
31 questions linked to/from How do you empty the buffers and cache on a Linux system?
21 votes
2 answers
177k views
How to clear memory cache in Linux [duplicate]
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.
10 votes
1 answer
8k views
What is equivalent to Mac's purge in Linux? [duplicate]
In Mac I use purge to free up some memory. What is equivalent to it in Linux(Ubuntu Server)? apt-get install purge gave me nothing. If you are no familiar with Mac's purge here is it's man page: ...
-1 votes
2 answers
6k views
Is there a way to free memory? [duplicate]
I remember, back from my days with Windows Vista/7, that there was a tool called memclear or memclean that would free some memory by invoking the NT garbage collection API. Probably it cleared cache ...
1 vote
0 answers
45 views
Cleaning cache (?) command du [duplicate]
Following this question I can reproduce that the first time I execute a du of a directory it takes longer than if I do it just after. Where is this caching happening? How can I clean it? I would like ...
111 votes
7 answers
139k views
Does rsync verify files copied between two local drives?
I want to make a fresh new copy of a large number of files from one local drive to another. I've read that rsync does a checksum comparison of files when sending them to a remote machine over a ...
132 votes
2 answers
304k views
Setting /proc/sys/vm/drop_caches to clear cache
As part of doing some cold cache timings, I'm trying to free the OS cache. The kernel documentation (retrieved January 2019) says: drop_caches Writing to this will cause the kernel to drop clean ...
57 votes
6 answers
9k views
How do I use swap space for emergencies only?
I have a Debian (Buster) laptop with 8 GB RAM and 16GB swap. I'm running a very long running task. This means my laptop has been left on for the past six days while it churns through. While doing ...
31 votes
3 answers
141k views
Memory runs full over time, high "buffer/cache" usage, low "available" memory
Whenever I reboot my laptop, everything runs amazingly and I have a maximum of 40% memory usage (out of 8GB). However over time (~ 1 day of usage), memory usage goes up to 90%+, and the system starts ...
20 votes
1 answer
65k views
"buff/cache" is very high, how I can free it? [duplicate]
The output of the top command shows that 29GB of memory is used by "buff/cache". What does it mean and how I can free it? It is near to 90% of memory.
13 votes
2 answers
5k views
Need something that is faster than "wc -l"
For a really big file like 1GB wc -l happens to be slow. Do we have a faster way calculating the number of newlines for a particular file?
33 votes
2 answers
3k views
Why did powering down my machine after a bad `rm` save my files?
Classical situation: I ran a bad rm and realized immediately afterwards that I had removed the wrong files. (Nothing critical and I had tolerably recent backups, but still annoying.) Knowing that ...
19 votes
2 answers
10k views
Linux: Total swap used = swap used by processes +?
So, I'm trying to do some investigation on where does swap use come from in a system with high swap usage: # free total used free shared buffers cached Mem: ...
7 votes
1 answer
20k views
What does -/+ buffers/cache means in the output of free? [closed]
I know this is a lame question, but I want to understand why CentOS consumes my Physical memory when certain process stopped. Suppose I have opened a file of 10GB then it consumes 10GB in ram and ...
8 votes
1 answer
7k views
List all files that are present in the cache
This question answers to the question on how to find the what is part of cache. However, in the fincore executable you have to pass the filename to check if it is part of cache. Is there a tools or a ...
1 vote
2 answers
9k views
Why doesn't Linux automatically clear caches?
Background My question is basically a follow-up to this question and answer, and in particular, this comment. Whenever I have to copy or rsync large amounts of files, the memory on my system tends ...
3 votes
3 answers
2k views
When is there a need to flush caches in Linux ?
I came across this . And then remembered seeing this something back. Could anybody elaborate is there any need for a user to ever flush the caches or it's only need is when you want to benchmark ...
0 votes
2 answers
4k views
How to disable the Linux page cache
The Linux kernel implements the page cache to accelerate I/O operations. It would be helpful to be able to turn off and on the page cache for research and testing. How can the Linux page cache be ...
3 votes
3 answers
3k views
Does sync command remove the dirty cache in the memory?
I am aware that sync command flushes the dirty cache into disk. I have run free command first, then sync, and then free again. The result of latter free command shows more free memory available than ...
3 votes
2 answers
2k views
Pipe Viewer - Progress monitor performance consequence
I am writing a batch script to sort through gigs and gigs of data. All of the data is text but the script will take a long long time to execute. I would like to give some visual indication that the ...
2 votes
3 answers
2k views
mmap and slow DMA transfers
I have a process that reads data from a hardware device using DMA transfers at a speed of ~4 * 50MB/s and at the same time the data is processed, compressed and written to a 4TB memory mapped file. ...
1 vote
1 answer
3k views
Is it safe to clear the buffers and cache on a linux server
After reading this link: How do you empty the buffers and cache on a Linux system?, I know that there are some commands that can help us to empty the buffers and cache of the OS. But I'm not sure if ...
2 votes
1 answer
4k views
How to analyze top command results: CPU & RAM consumption
I am working on ARM-based processor (OS version: Linux 3.4.35) and I need to analyze the processor's performance while some processes are running, by typing top command, I can see some statistics but ...
-4 votes
1 answer
1k views
How does echoing an echo not just echo in a cronjob?
I'm reading this article on clearing buffer/cache from my new Linux VMs since they're taking a full 1/3rd of my RAM, so I ran this: sync; echo 1 > /proc/sys/vm/drop_caches This immediately fixed ...
0 votes
1 answer
2k views
Buffer memory increased
My buffer memory in server got increased after taking backups from multiple servers using rsync. This disk got almost full, removed the backups. As far as I understand buffers shoot up if we perform a ...
0 votes
1 answer
2k views
Linux Cache cannot be cleared completely, it fills the entire RAM after some days
I use a laptop for work and therefore I only do a suspend to RAM rather than shutdown everyday. so I do not have to start each application again every day. after some days of "run time" I ...
1 vote
1 answer
1k views
Reading stale file data with debugfs cat
I'm trying to read the contents of a file using the file's inode. This works fine: echo "First line" > data.txt sync sudo debugfs -R "cat <$(stat -c %i data.txt)>" /dev/...
4 votes
4 answers
554 views
How can I optimize this Unix command?
The following command takes about 10 minutes to output the result find . -name "muc*_*_20160920_*.unl*" | xargs zcat | awk -F "|" '{if($14=="20160920100643" && $22=="567094398953") print $...
1 vote
2 answers
1k views
Clean RAM after some days of PC usage
I have 8GB RAM, and use my PC (Debian 10, KDE plasma 5.14.5) "normally" but with many programs running in parallel: Firefox (≈ 250 Tabs) Chromium (10 Tabs) Thunderbird 10x Okular 2x Pycharm ...
2 votes
0 answers
1k views
How do I figure out what is consuming memory?
I develop a system (x86_64 based) that runs Linux (Ubuntu 14.04.3) and has several pieces of custom built hardware connected. I have written drivers and control software for the custom hardware. ...
1 vote
1 answer
394 views
How does the diff command handle caching?
I became curious when I was diffing two large (>326MB) files, and noticed that the second run took much less time than the first. This was frustrating, since I was trying to time the second run, to ...
4 votes
1 answer
525 views
Disable buffering in a VM configuration
I am executing some benchmark using a DBMS and virtual machines. And I am using this command free && sync && echo 3 > /proc/sys/vm/drop_caches && free on each Guest, and on ...