feat(facade): Limit request cache using runtime flag #793
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dranikpg
approved these changes
Feb 13, 2023
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| ABSL_FLAG(std::uint64_t, request_cache_limit, 1ULL << 26, // 64MB | ||
| "Amount of memory to use for request cache in bytes - per IO thread."); | ||
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I thought we had those postifxes for memory sizes 😄
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what do you mean @dranikpg ?
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| // Gradually release the request pool. | ||
| // The request pool is shared by all the connections in the thread so we do not want | ||
| // to release it aggressively just because some connection is running in | ||
| // non-pipelined mode. So we wait at least N times, | ||
| // where N is the number of connections in the thread. | ||
| if (!free_req_pool_.empty()) { | ||
| free_req_pool_.pop_back(); | ||
| ++free_req_release_weight; | ||
| if (free_req_release_weight > stats_->num_conns) { | ||
| free_req_release_weight = 0; | ||
| stats_->pipeline_cache_capacity -= free_req_pool_.back()->StorageCapacity(); | ||
| free_req_pool_.pop_back(); | ||
| } |
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I forgot, do you release them to reduce memory usage after peaks? Or for some other reason?
Your current mechanism doesn't look very reliable for this case 🤔
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The reason is pragmatic. I want to keep the cache if it's needed and free it if it's not. This heuristic is simple, indeed, but it will gradually release the cache if it's not being used, and since we share it among all connections Dragonfly won't overallocate it.
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