See how to read per-zone information to find fragmentation, low watermarks and reclaim candidates. 30.12.2025 | reading time: 2 min Memory in Linux is split into zones such as DMA, Normal, HighMem and Movable; read those zones to find where free pages and watermarks sit and to spot fragmentation quickly. Run a live inspection Run `grep -A6 'Node 0, zone Normal' /proc/zoneinfo` to focus on one zone; for example execute the following to view a snippet and its meaning: ``` grep -A6 'Node 0, zone Normal' /proc/zoneinfo ```and you might see output like: ``` Node 0, zone Normal zone start PFN 524288 pages free 12345 pages active 67890 pages inactive 2345 managed 64512 ```Check the "pages free" line to see how many free pages exist in that zone and compare with the zone watermarks to decide if the kernel is struggling to satisfy allocations. What to look for next Look at watermarks and "pages free" across zones; if Normal is low while HighMem has plenty, a 32bit or device DMA constraint is indicated; a steady drop in free pages during heavy allocation hints at fragmentation and you should check compaction and migration settings or enable the Movable zone for hotplugged memory. Practical follow-ups Correlate zone info with `vmstat` or `free` to see overall pressure, use `numactl` to test NUMA placement, and run memory compaction or adjust `zone_reclaim_mode` only after measuring; always reproduce the issue in a test system before tuning production. Where this helps Inspecting zones is useful when drivers fail to allocate DMA memory, when big contiguous allocations fail, or when the OOM killer targets processes despite plenty of total RAM; read the zone entries, reproduce the allocation pattern, then act. Final thought Knowing how to read /proc/zoneinfo turns vague memory complaints into focused actions; keep practicing, tie this skill into troubleshooting workflows and consider deepening knowledge with certificate training at bitsandbytes.academy. Join Bits & Bytes Academy First class LINUX exam preparation. utilities boot-process processes troubleshooting
