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fix: handle corner case when comitted memory is negative (#570)

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Set mem_defrag_threshold so that defrag will be trigerred when memory grows.

Signed-off-by: Roman Gershman <roman@dragonflydb.io>

Signed-off-by: Roman Gershman <roman@dragonflydb.io>
This commit is contained in:
Roman Gershman 2022-12-19 13:56:20 +02:00 • committed by GitHub
parent 5f572f00f1
commit cdc31fc98c
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1 changed files with 7 additions and 6 deletions
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13
src/server/engine_shard_set.cc
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@ -31,9 +31,8 @@ ABSL_FLAG(bool, cache_mode, false,
"by evicting entries when getting close to maxmemory limit");
// memory defragmented related flags
ABSL_FLAG(float, mem_defrag_threshold,
1, // The default now is to disable the task from running! change this to 0.05!!
"Minimum percentage of used memory relative to total available memory before running "
ABSL_FLAG(float, mem_defrag_threshold, 0.7,
"Minimum percentage of used memory relative to maxmemory cap before running "
"defragmentation");
ABSL_FLAG(float, commit_use_threshold, 1.3,
@ -80,20 +79,22 @@ EngineShard::Stats& EngineShard::Stats::operator+=(const EngineShard::Stats& o)
// 3. in case the above is OK, make sure that we have a "gap" between usage and commited memory
// (control by commit_use_threshold flag)
bool EngineShard::DefragTaskState::IsRequired() const {
const uint64_t threshold_mem = max_memory_limit * GetFlag(FLAGS_mem_defrag_threshold);
const int64_t threshold_mem = max_memory_limit * GetFlag(FLAGS_mem_defrag_threshold);
const double commit_use_threshold = GetFlag(FLAGS_commit_use_threshold);
if (cursor > kCursorDoneState) {
return true;
}
uint64_t commited = GetMallocCurrentCommitted();
// can be negative due to weird accounting of mimalloc.
int64_t commited = GetMallocCurrentCommitted();
uint64_t mem_in_use = used_mem_current.load(memory_order_relaxed);
// we want to make sure that we are not running this to many times - i.e.
// if there was no change to the memory, don't run this
if (threshold_mem < commited && mem_in_use > 0 &&
(uint64_t(mem_in_use * commit_use_threshold) < commited)) {
(uint64_t(mem_in_use * commit_use_threshold) < uint64_t(commited))) {
// we have way more commited then actual usage
return true;
}