Why my CentOS droplet is eating all the RAM memory?
I started with a 2vCPU 2GB CentOS 7 x64 droplet installed from marketplace with a Plesk image. I have only create a Wordpress website with no more than 400 visits per month and followed the initial server setup for CentOS 7 on DigitalOcean.
Then I have started getting alerts from the DigitalOcean monitoring service because the droplet was using more than 70% of memory. I receive those mails 7 times per day, memory usage and resolved ones.
So I thought I was running out of memory, then I have purchased 2GB extra. So my droplet is now a 2vCPU 4GB. After 3 days, same as before, the alert emails for memory beyond 70% started to get my inbox.
At this particular moment, the server is upside that 70% of memory so I ran the command I know DigitalOcean uses to calculate memory (https://www.digitalocean.com/docs/monitoring/resources/glossary-of-terms/#memory)
The results are:
MemTotal: 3880364 kB MemFree: 287080 kB MemAvailable: 2561780 kB Buffers: 32 kB Cached: 994716 kB SwapCached: 0 kB Active: 1224116 kB Inactive: 455532 kB Active(anon): 769364 kB Inactive(anon): 27284 kB Active(file): 454752 kB Inactive(file): 428248 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 16 kB Writeback: 0 kB AnonPages: 684948 kB Mapped: 101816 kB Shmem: 111748 kB Slab: 1750432 kB SReclaimable: 1678876 kB SUnreclaim: 71556 kB KernelStack: 5552 kB PageTables: 17372 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 1940180 kB Committed_AS: 3978072 kB VmallocTotal: 34359738367 kB VmallocUsed: 95708 kB VmallocChunk: 34359537660 kB HardwareCorrupted: 0 kB AnonHugePages: 344064 kB CmaTotal: 0 kB CmaFree: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 98276 kB DirectMap2M: 4096000 kB DirectMap1G: 0 kB
free -m results are:
total used free shared buff/cache available Mem: 3789 935 240 109 2613 2464 Swap: 0 0 0
Plesk on the other side, trough Grafana is telling me that
memory:memory-used:value 858 Mb
memory:memory-cached:value 971 Mb
memory:memory-slab_recl:value 1.6 Gb
Any ideas? Anything that would help me understand this situation and solve it?