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a61ff53150
"The current criteria for memtable flush is not being respected. The problem is demonstrated to happen when the dirty memory group is over limit, and so is the system table extra allowance. In that situation, both the normal region and the system table region will be under pressure and try to flush. More specifically, because the normal region inherits from the system region, if the normal region is under pressure (over the soft limit threshold), the system region will certainly be as well, even though it has an extra allowance. This is because after virtual dirty, we start blocking when we reach half the region, but memory itself can grow up to 100 % of the region. So the total amount of memory used will be certainly bigger than the system pressure threshold, which is now 50 % plus the allowance. To fix that, this patch reworks the flush logic so that the regions are not dependent on each other. Fixes #1918" * 'flush-criteria-v6' of github.com:glommer/scylla: config: get rid of memtable_total_space database: rework dirty memory hierarchy system keyspace: write batchlog mutation in user memory database: remove flush_token database: abstract pressure condition notification database: encapsulate semaphore_units into a flush_permit database: remove friendship declaration database: simplify flush_one database: make memtable_list aware in cases it can't flush