Re: [Internet]Re: [PATCH v3] acl: support custom memory allocator

[=?gb18030?B?bWFubnl3YW5nKM3108C35Sk=?= <mannywang@tencent.com>]

Thanks for sharing this suggestion.

We actually evaluated the heap-based approach before implementing this 
patch.
It can help in some scenarios, but unfortunately it does not fully solve our
use cases. Specifically:

1. **Heap count / scalability**
    Our application maintains at least ~200 rte_acl_ctx instances (due 
to the
    total rule count and multi-tenant isolation). Allowing a dedicated 
heap per
    context would exceed the practical limits of the current rte_malloc heap
    model. The number of heaps that can be created is not unlimited, and
    maintaining hundreds of separate heaps would introduce considerable
    management overhead.

2. **Temporary allocations in build stage**
    During `rte_acl_build`, a significant portion of memory is allocated 
through
    `calloc()` for internal temporary structures. These allocations are 
freed
    right after the build completes. Even if runtime memory could come 
from a
    custom heap, these temporary allocations would still need an independent
    allocator or callback mechanism to avoid fragmentation and repeated
    malloc/free cycles.

The goal of this patch is to provide allocator callbacks so that 
applications
can apply their own memory model consistently — static region for 
runtime, and
resettable pool for build — without relying on uncontrolled internal
allocations.

On 11/26/2025 2:01 AM, Dmitry Kozlyuk wrote:
> On 11/25/25 15:14, mannywang(王永峰) wrote:
>> Reduce memory fragmentation caused by dynamic memory allocations
>> by allowing users to provide custom memory allocator.
>>
>> Add new members to struct rte_acl_config to allow passing custom
>> allocator callbacks to rte_acl_build:
>>
>> - running_alloc: allocator callback for run-time internal memory
>> - running_free: free callback for run-time internal memory
>> - running_ctx: user-defined context passed to running_alloc/free
>>
>> - temp_alloc: allocator callback for temporary memory during ACL build
>> - temp_reset: reset callback for temporary allocator
>> - temp_ctx: user-defined context passed to temp_alloc/reset
>>
>> These callbacks allow users to provide their own memory pools or
>> allocators for both persistent runtime structures and temporary
>> build-time data.
>>
>> A typical approach is to pre-allocate a static memory region
>> for rte_acl_ctx, and to provide a global temporary memory manager
>> that supports multipleallocations and a single reset during ACL build.
>>
>> Since tb_mem_pool handles allocation failures using siglongjmp,
>> temp_alloc follows the same approach for failure handling.
> 
> If a static memory region would suffice for runtime memory,
> could you have solved the issue using existing API as follows?
> 1. Allocate memory in any way, may even use `rte_malloc_*()`.
> 2. Create a new heap using `rte_malloc_heap_create()`.
> 3. Attach the memory to the heap using `rte_malloc_heap_memory_add()`.
> 4. Get the heap "socket ID" using `rte_malloc_heap_get_socket()`.
> 5. Pass the heap "socket ID" to `rte_acl_create()`.
> 
> In https://inbox.dpdk.org/dev/tencent_4125B1322F9238892BFA5F38@qq.com/
> you said that the issue is runtime memory fragmentation,
> but also did "propose extending the ACL API to support
> external memory buffers for the build process".
> What is the issue with build-time allocations?
> 
>