Unexpected high file open ops

[JaySon-Huang]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

2. What did you expect to see? (Required)

3. What did you see instead (Required)

We get an unexpected high file open ops after running for a period

BlobStore::getBlobFile likely go into the miss branch

After restarted, the file open ops become normal

BlobStore::getBlobFile go into the hit branch

4. What is your TiFlash version? (Required)

v6.4.0

[JaySon-Huang]

Track in another issue 6347 Another problem is the cpu and memory reported by tiflash-proxy is abnormal 

[JaySon-Huang]

profile_2022-11-22_10-32-00.zip

[JaySon-Huang]

[JaySon-Huang]

The root cause is LRUCache::remove does not update current_size. So that after lots of getOrSet and remove, removeOverflow will make the LRUCache only keep 1 element.

tiflash/dbms/src/Common/LRUCache.h

Lines 143 to 153 in f121236

	void remove(const Key & key)
	{
	std::lock_guard cache_lock(mutex);
	auto it = cells.find(key);
	if (it == cells.end())
	return;
	Cell & cell = it->second;
	queue.erase(cell.queue_iterator);
	cells.erase(it);
	}