Glusterfs Session #8 discusses memory tracking infrastructure in Gluster to identify memory leaks, using statedumps to analyze leaking structures, how io-thread bricks scale with file operations, and future improvements for io-threads. Specifically, it outlines how Gluster enumerates data structures to track memory allocations and deallocations, how statedumps can be interpreted to find leaks, why io-threads are used and how they could prioritize different operation priorities or use thread pools.

1. Glusterfs Session #8
Memory tracking infra, io-threads

2. Scope
- How memory tracking is done to identify memory leaks in gluster
- How to use statedumps to identify the structures that are leaking memory
- How bricks processes scale with the number of fops
- Future improvements that can be done in io-threads.

3. Memory tracking infra
- Idea is to give enumerate all the data structures that will be used in an xlator
and let the memory allocation/deallocation functions to increment/decrement
the numbers as and when allocation/deallocations happen.
- Xlators can create mem_acct_init function to add its own data structures that
are used in that particular xlator.
- GF_CALLOC does increments of counts at the time of allocations.
- GF_FREE does decrements of counts at the time of de-allocations.

4. Memory tracking infra - Continued
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Actual Data Trailer

5. How to use statedump to identify leaks
- Example of how leaks are identified
https://github.com/gluster/glusterfs/issues/2337
- Interpreting statedump output
- [global.glusterfs - usage-type gf_common_mt_xlator_t memusage]
- size=42240
- num_allocs=10
- max_size=42240
- max_num_allocs=10
- total_allocs=10

6. io-threads
- Why do we need an xlator like io-threads?
- How does it work?
- How can we improve latencies for different priorities of fops?
- Code walkthrough

7. Io-threads future directions
- Io-uring
- Thread pool implementations

8. Q & A