Linux buddyinfo
From Leo's Notes
Last edited on 20 November 2023, at 22:35.
In Linux, understanding the output of /proc/puddyinfo is helpful when diagnosing memory issues.
Example output[edit | edit source]
On a Linux system with 3TB of memory installed, this is what /proc/buddyinfo looks like:
# cat /proc/buddyinfo | column -t
Node 0, zone DMA 0 0 0 0 0 0 0 0 1 1 2
Node 0, zone DMA32 3 4 4 1 3 1 3 3 3 2 360
Node 0, zone Normal 5987 3535 15411 2939 990 227 110 56 296 0 0
Node 1, zone Normal 340611 348961 3195042 3452371 461840 13472 673 58 1 0 0
Node 2, zone Normal 8662816 6463200 5923202 2292623 299873 23766 10924 5156 1101 3 54266
Node 3, zone Normal 167 322 153 437 249 134 69 42 27 6 188034
A few keypoints to understand from this output:
- Each Node represents a CPU
- There are 3 types of zones.
- On 64bit systems, DMA references the first 16MB, DMA32 is 16MB - 4GB and lower, and Normal is everything after 4GB.
- Each column represents the number of available pages of a particular size. Intel systems have a memory page size of 4096 bytes (run
getconf PAGESIZE)- 1st column: 2^0 * PAGE SIZE. 4k
- 2nd column: 2^1 * PAGE SIZE. 8k
- 3rd column: 2^2 * PAGE SIZE. 16k
- 4th column: 2^3 * PAGE SIZE. 32k
- 5th column: 2^4 * PAGE SIZE. 64k
- ...
- 11th column: 2^10 * PAGE SIZE. 4M