Linux memory
Links
- Linux ate my RAM!
- How to Clear RAM Memory Cache, Buffer and Swap Space on Linux
- How to interpret output from Linux 'top' command?
- Understanding VM swappiness
- What is swappiness on Linux
- https://www.kernel.org/doc/html/latest/filesystems/proc.html The /proc Filesystem]
- Swappiness in Linux: Everything you need to know
- https://serverfault.com/questions/85470/meaning-of-the-buffers-cache-line-in-the-output-of-free
- Memory Consumption in Linux
- Difference between Paging and Swapping
- Why is system using swap when there is enough free space in ram?
- Linux page cache basics
/proc/meminfo
Documentation
Output of 'free' command
available
MemAvailable in /proc/meminfo
man 5 proc
see /proc/meminfo
total
Is MemTotal in /proc/meminfo
Total usable ram (i.e. physical ram minus a few reserved bits and the kernel binary code)
used
total - free - buffers - cache
unused
MemFree
RSS
Resident Set Size
RSS and VSZ in Linux memory management
"memory is allocated to that process and is in RAM. It does not include memory that is swapped out. It does include memory from shared libraries as long as the pages from those libraries are actually in memory. It does include all stack and heap memory."
VSZ / VmSize
Virtual Memory Size It includes all memory that the process can access, including memory that is swapped out, memory that is allocated, but not used, and memory that is from shared libraries.
ZFS and arc
Tools
- arc_summary
Links
Changing arc sizes in runtime
#in bytes echo 1024 > /sys/module/zfs/parameters/zfs_arc_min echo 2048 > /sys/module/zfs/parameters/zfs_arc_max
Changing arc settings
In /etc/modprobe.d/zfs.conf:
options zfs zfs_arc_max=4294967296 options zfs zfs_arc_min=1073741824
If root on ZFS (really?)
update-initramfs -u -k all
FAQ
What is using all my memory?
smem -r -s swap| head -n3
What is using all my swap?
https://www.cyberciti.biz/faq/linux-which-process-is-using-swap/
for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | less
or to just list top 3
for file in /proc/*/status ; do awk '/VmSwap|Name/{printf $2 " " $3}END{ print ""}' $file; done | sort -k 2 -n -r | head -n 3
Watch buffer/cache activity
https://www.heroix.com/blog/linux-memory-use/
sar -B
What is in buffer/cache?
Tools
Clear buffer/cache
sync; echo 3 > /proc/sys/vm/drop_caches
