Hi, We see an odd pattern where InnoDB buffer pool usage drops regularly. Attached are two screenshots of memory usage on an 11.4.4 node: one at 20:15 with an InnoDB buffer pool of 47,5 GiB, and 5 minutes later with a 3,69 GiB one. The times at which this occurs are -seemingly- random. Other internal memory structures are stable. On at least one node with this issue, the InnoDB buffer pool is smaller (48 GiB) than the sum of data + indexes (87,57 GiB). As far as I can see (graphing history is limited), this has started occurring after upgrading from MariaDB 10.11.9 to 10.11.10 and from 11.4.3 to 11.4.4 respectively. At first sight, in the pre-release notes for 10.11.11 and 11.4.5, I don't see any related issues. To make absolutely sure this is related to the upgrade, we will be downgrading a troubled node tonight, to see if it fixes anything. I will report back. In userland, these drops cause a domino effect: no cache -> more I/O -> slower queries -> nuisance in application. Has anyone else seen this pattern, possibly after upgrading to the aforementioned versions? Although 1) neither of these versions are bleeding edge and 2) I haven't seen any such reports, asking is worth a shot as this started occurring on several machines after upgrading with no configuration nor (obvious) usage changes. With kind regards, William David Edwards
