I wanted to know the concept of free -m command as there are different rows of Mem, -/+ buffers/cache & Swap in the output. As an example, it is showing 195 as free Mem in my server but 13850 in the free section of the -/+ buffers/cache row. The output needs in depth knowledge of the different parameters of the command.
The free command is used to display the amount of free and used memory on a system. The -m option tells free to print the output in MB.
My laptop has 4Gb currently.
Linux attempts to utilize all of the memory on the system and not leave any sitting idle, like some other operating systems have done over time. Memory will be used for the OS and applications, but the remainder will be used as "buffers and cache". The kernel will keep items in memory that are needed often or are predicted to be needed for faster access. The memory used for "buffers and cache" is available for applications or the OS to use. If required, it is quickly flushed and used.
To find the actual available memory on my system, take the last number on the Mem line (247) and add it to the last number on the Mem line (2397). So currently, I have about 3G of memory available.
Most of this information is available via the manpage and simple google searches. Take a look and you should have all of your questions answered.
Thanks for your answer. I wanted to add something, if we add 118 to the total of 2397 & 247, it would be 2762 which is very near the free memory on line 2, 2763. Please confirm on this.
Also, as per your answer, the architecture of Linux is to utilize all the memory on the system.
the line +/- buffers/cache basically shows the memory used and free without taking into account how much is used for buffers or cache.
This is because cached memory is not actually used memory, it is information that is stored for quick retrieval if requested again from previous operations but dumped straight away if memory is required to be written to. This process makes the system run quicker as queries are using data stored on RAM instead of hard disk which is obviously a much quicker process.
Thanks for your answer. Does it mean that if it is a 64 bit kernel, it could use even 40 GB if the laptop has that much memory? Also, does it mean that a PAE kernel would use maximum of 64 GB of memory even if the laptop/ machine had 128 GB of memory?
I hope my queries are clear that
1) A 64 bit kernel would use even upto 40 GB of memory if I increased the laptop memory to 40 from 8 GB.
2) A PAE kernel would use only 64 GB of memory even if the laptop/machine had 128 GB of memory.
I have two questions on Linux's free command. Below, I have provided output from my home laptop (fedora 26 ) which has 16GB Physical RAM and a production server (RHEL 7.4) which has 24GB RAM.
Question1. What exactly does the buffer/cache column say in free command's output ? buffer/cache is... (9 Replies)
hi- im running glassfish 3.1 on debian server and there are times where I need to start the domain when we cannot access the web application. I checked the memory and it's confusing me. Am i still ok? can you explain the below?
USER PID %CPU %MEM VSZ RSS TTY STAT START TIME... (1 Reply)
Hello, I am not sure where to post this questions...
I have Windows XP in my home computer. I need to install Linux on
my home computer for learning purpose. Can one please recommend
any free download link to download free linux...
Any help is appreciated...
Thank you... (1 Reply)
Hi,
I am facing one problem, On our Linux server Free memory decreases gradually but my java process memory does not increase.
Please any one tell, why free memory decreases gradually (1MB in approx 15 minutes).
kernel details:-
Linux linux4 2.6.9-42.ELsmp #1 SMP Wed Jul 12 23:27:17 EDT... (13 Replies)
Hi All,
Please explain me the concept of link counts when you try to view the contents of any file or directory using ls command.
-sh-3.00$ ls -lrt
total 194
drwxr-xr-x 2 root root 4096 Aug 12 2004 srv
drwxr-xr-x 2 root root 4096 Aug 12 2004 mnt
drwxr-xr-x 2 root root ... (1 Reply)
Linux Kernels 2.6.16 and up provide a way to instruct the kernel to drop the page cache, inode and dentry caches on command. This tip can help free Linux memory without a reboot.
Note: This is a non-destructive operation. Dirty objects are not freeable, hence; you must run sync beforehand.
... (0 Replies)
HI
I'm a rookie in C programming and I'm working in Monta Vista Linux. I have to write a program that displays free memory. I have memtester(allready written by someone else) and now I have to type how much amount of memory tester will test and I want that memtester finds out himself how much of... (11 Replies)
CentOS 2 and 3 are a 100% compatible rebuild of the RHEL 2 and 3 versions, in full compliance with RedHat's redistribution requirements. It is for people who need an enterprise class OS without the cost of certification and support.
Read more here.
I've just installed it on a spare box and it... (0 Replies)
I know that free command displays memory usages however I like to know how the option and the results when I use this command..
PLease respond ASAP
thanx... I am a newbie.. :D (1 Reply)