[pull] master from netdata:master

[pull]

See Commits and Changes for more details.

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Created by pull[bot] (v2.0.0-alpha.1)

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Summary by Sourcery

Enhancements:

• Optimize element allocation in the ARAL allocator to reduce contention and improve throughput.

[sourcery-ai]

Reviewer's Guide by Sourcery

This pull request introduces a per-CPU free list to the ARAL allocator, aiming to reduce contention on the global free list lock. This is achieved by partitioning the incoming free list and using a bitmap to track available partitions. The change also includes a fast path for allocating new elements, using atomic operations to avoid locking when possible.

Sequence diagram for optimized memory allocation

sequenceDiagram
    participant C as Client
    participant A as ARAL Allocator
    participant P as ARAL Page

    C->>A: Request memory allocation
    A->>P: Try fast path allocation
    alt Fast path successful
        P-->>A: Return new segment
        A-->>C: Return memory
    else Fast path failed
        P->>P: Lock available list
        P->>P: Check incoming partitions
        P->>P: Get free slot from partition
        P-->>A: Return reused memory
        A-->>C: Return memory
    end

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Class diagram showing ARAL page structure changes

classDiagram
    class ARAL_PAGE {
        +const char* filename
        +uint8_t* data
        +bool marked
        +bool started_marked
        +bool mapped
        +uint32_t size
        +uint32_t max_elements
        +uint64_t elements_segmented
        +uint32_t incoming_partition_bitmap
    }
    note for ARAL_PAGE "Changed structure layout and added partitioned incoming list"

    class ARAL_FREE {
        +size_t size
        +ARAL_FREE* next
    }

    ARAL_PAGE --> ARAL_FREE : has multiple incoming[4]

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State diagram for ARAL memory allocation states

stateDiagram-v2
    [*] --> TryFastPath
    TryFastPath --> NewSegment: Slot < max_elements
    TryFastPath --> CheckAvailable: Slot >= max_elements
    CheckAvailable --> LockPartition: No available list
    CheckAvailable --> ReuseMemory: Has available list
    LockPartition --> ReuseMemory: Get from partition
    NewSegment --> [*]: Return memory
    ReuseMemory --> [*]: Return memory

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File-Level Changes

Change	Details	Files
Introduced per-CPU free lists to reduce lock contention.	Partitioned the incoming free list into ARAL_PAGE_INCOMING_PARTITIONS separate lists. Added a bitmap (incoming_partition_bitmap) to track available partitions. Modified aral_add_free_slot___no_lock_required to add free slots to a partition based on the current thread ID. Modified aral_get_free_slot___no_lock_required to check for available partitions and retrieve free slots from them. Added a fast path in aral_get_free_slot___no_lock_required to allocate new elements using atomic operations, avoiding locking when possible if the page isn't full	src/libnetdata/aral/aral.c
Added a fast path for allocating new elements using atomic operations.	Added elements_segmented to ARAL_PAGE to track the number of elements allocated using the fast path. Modified aral_get_free_slot___no_lock_required to use elements_segmented for allocating new elements without locking when possible if the page isn't full	src/libnetdata/aral/aral.c

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