On Wed, 15 Apr 2026 01:08:18 +0530 Vipin Varghese <[email protected]> wrote:
> This series introduces a topology library that groups DPDK lcores based on > CPU cache hierarchy and NUMA topology. The goal is to provide a stable and > explicit API that allows applications to select lcores with better locality > and cache sharing characteristics. > > The series includes: > - EAL support for topology discovery using hwloc and domain-based lcore > grouping (L1/L2/L3/L4/NUMA) > - Topology-aware test cases validating API behavior and edge conditions > - Programmer’s guide describing the topology library and APIs > > The API is marked experimental and does not change existing lcore behavior > unless explicitly used by the application. > > Changes in v5: > - Addressed review comments from v4 > - Fixed ARM cross-compilation issues > - Cleaned up domain iteration and error handling > - Updated tests to cover domain edge cases > - Documentation refinements and API usage clarification > > Changes in v4: > - Corrected domain selection semantics > - Updated example usage > - Fixed naming and typo issues > > Changes in v3: > - Fixed macro naming (USE_NO_TOPOLOGY) > - Minor cleanups based on early feedback > > Tested on: > - AMD EPYC (Milan, Genoa, Siena, Turin, Turin-Dense, Sorano) > - Intel Xeon (SPR-SP, GNR-SP) > - ARM Ampere > - NVIDIA Grace Superchip > > Dependencies: > - hwloc-dev (tested with 2.10.0) > > Patch breakdown: > 1/3 eal/topology: add topology grouping for lcores > 2/3 app: add topology-aware test cases > 3/3 doc: add topology library documentation > > Future Work: > - integrate into examples > -- hellowrld: ready > -- pkt-distributor: in-progress > -- l2fwd: ready > -- l3fwd: to start > -- eventdevpipeline: PoC ready > - integrate topology test > -- crypto: yet to start > -- compression: yet to start > -- dma: PoC ready > - add new features for > -- PQoS: yet to start > -- Data Injection: PoC with BRDCM Thor-2 ready > > Tested OS: Linux only, need help with BSD and Windows > > Tested with and without hwloc-dev library for > - Ampere, aarch64, Neoverse-N1, NUMA-2, 256 CPU threads > - Grace superchip, aarch64, Neoverse-V2, NUMA-2, 144 CPU threads > - Intel GNR-SP, 6767P, NUMA-2, 256 Threads > - AMD EPYC Siena, 8534P, NUMA-1, 128 Threads > - AMD EPYC Sorano, 8635P, NUMA-1, 168 Threads > > Signed-off-by: Vipin Varghese <[email protected]> > `` > > Vipin Varghese (3): > eal/topology: add Topology grouping for lcores > app: add topology aware test case > doc: add new section topology > > app/test/meson.build | 1 + > app/test/test_ring_perf.c | 416 +++++++++++++- > app/test/test_stack_perf.c | 409 ++++++++++++++ > app/test/test_topology.c | 676 ++++++++++++++++++++++ > config/meson.build | 18 + > doc/api/doxy-api-index.md | 1 + > doc/guides/prog_guide/index.rst | 3 +- > doc/guides/prog_guide/topology_lib.rst | 155 +++++ > lib/eal/common/eal_private.h | 74 +++ > lib/eal/common/eal_topology.c | 747 +++++++++++++++++++++++++ > lib/eal/common/meson.build | 1 + > lib/eal/freebsd/eal.c | 10 +- > lib/eal/include/meson.build | 1 + > lib/eal/include/rte_topology.h | 255 +++++++++ > lib/eal/linux/eal.c | 7 + > lib/eal/meson.build | 4 + > 16 files changed, 2773 insertions(+), 5 deletions(-) > create mode 100644 app/test/test_topology.c > create mode 100644 doc/guides/prog_guide/topology_lib.rst > create mode 100644 lib/eal/common/eal_topology.c > create mode 100644 lib/eal/include/rte_topology.h > AI review reported lots of possible correctness problems: # DPDK Patch Review - bundle-1843-topology-v5.mbox ## Overview This patch series introduces topology awareness to DPDK, allowing applications to select logical cores based on CPU cache and I/O topology. The series adds a new `rte_topology` library with APIs to query and enumerate logical cores within topology domains (L1/L2/L3/L4/NUMA). --- ## Correctness Bugs (HIGHEST PRIORITY - report at >=50% confidence) ### Patch 1/3: lib/eal/common/eal_topology.c #### **Error: Resource leak on `eal_topology_map_layer()` failure** In `rte_eal_topology_init()`, if any call to `eal_topology_map_layer()` fails (returns < 0), the code calls `rte_eal_topology_release()` which frees previously allocated layers. However, the `hwloc_topology_t` handle `topo_cnfg.topology` is **NOT** destroyed before returning. This leaks the hwloc topology handle. **Location:** `lib/eal/common/eal_topology.c:685-712` ```c for (int i = 0; i < 5; i++) { *layers[i].count = hwloc_get_nbobjs_by_depth(topo_cnfg.topology, layers[i].depth); if (eal_topology_map_layer(topo_cnfg.topology, layers[i].depth, layers[i].count, layers[i].ptr, layers[i].total_cores, layers[i].name) < 0) { rte_eal_topology_release(); /* frees layer memory */ return -1; /* BUG: topo_cnfg.topology NOT destroyed here */ } } hwloc_topology_destroy(topo_cnfg.topology); /* only reached on success */ topo_cnfg.topology = NULL; ``` **Fix:** Destroy the topology before returning on error: ```c if (eal_topology_map_layer(...) < 0) { hwloc_topology_destroy(topo_cnfg.topology); topo_cnfg.topology = NULL; rte_eal_topology_release(); return -1; } ``` --- #### **Error: Potential use-after-free in `eal_topology_map_layer()` on partial allocation failure** In `eal_topology_map_layer()`, the code allocates `dm->cores` for each domain. If a later allocation in the same loop iteration fails (e.g., for domain `j+1`), the function returns -1 immediately **without freeing `dm->cores` already allocated for earlier domains**. The caller (`rte_eal_topology_init()`) then calls `rte_eal_topology_release()`, which expects `layer_ptr[j]` to be non-NULL but `layer_ptr[j]->cores` may be uninitialized or garbage if the allocation failed before that point. This can cause a use-after-free or double-free when `rte_eal_topology_release()` calls `rte_free(d->map[i]->cores)`. **Location:** `lib/eal/common/eal_topology.c:537-557` ```c for (uint16_t j = 0; j < *layer_cnt; j++) { hwloc_obj_t obj = hwloc_get_obj_by_depth(topology, depth, j); int cpu_count = hwloc_bitmap_weight(obj->cpuset); if (cpu_count == -1) continue; struct core_domain_mapping *dm = rte_zmalloc(NULL, sizeof(struct core_domain_mapping), 0); if (!dm) return -1; /* BUG: leaks layer_ptr array allocated by caller */ (*layer_ptr)[j] = dm; CPU_ZERO(&dm->core_set); dm->core_count = 0; dm->cores = rte_malloc(NULL, sizeof(uint16_t) * cpu_count, 0); if (!dm->cores) return -1; /* BUG: leaks dm (just allocated) and previous entries */ } ``` **Fix:** On allocation failure, free all previously allocated entries before returning: ```c if (!dm) { /* Free all previously allocated entries */ for (uint16_t k = 0; k < j; k++) { if ((*layer_ptr)[k]) { rte_free((*layer_ptr)[k]->cores); rte_free((*layer_ptr)[k]); } } rte_free(*layer_ptr); return -1; } /* Same cleanup for dm->cores allocation failure */ if (!dm->cores) { rte_free(dm); for (uint16_t k = 0; k < j; k++) { if ((*layer_ptr)[k]) { rte_free((*layer_ptr)[k]->cores); rte_free((*layer_ptr)[k]); } } rte_free(*layer_ptr); return -1; } ``` --- #### **Error: NULL pointer dereference in `eal_topology_map_layer()` when `hwloc_get_obj_by_depth()` returns NULL** In the second loop of `eal_topology_map_layer()` (lines 560-620), the code calls `hwloc_get_obj_by_depth(topology, depth, j)` and checks `if (!obj || hwloc_bitmap_iszero(obj->cpuset))` to skip NULL objects. However, in the **inner loop** (lines 579-618), the code calls `hwloc_get_obj_by_depth(topology, depth, k)` and assigns it to `obj_core` but does **NOT** check if `obj_core` is NULL before calling `hwloc_bitmap_weight(obj_core->cpuset)` on line 581. If `hwloc_get_obj_by_depth()` returns NULL for domain `k`, this will dereference a NULL pointer. **Location:** `lib/eal/common/eal_topology.c:579-582` ```c for (uint16_t k = 0; k < *layer_cnt; k++) { hwloc_obj_t obj_core = hwloc_get_obj_by_depth(topology, depth, k); int cpu_count_core = hwloc_bitmap_weight(obj_core->cpuset); /* NULL deref if obj_core == NULL */ if (cpu_count_core == -1) continue; ``` **Fix:** Check `obj_core` before dereferencing: ```c hwloc_obj_t obj_core = hwloc_get_obj_by_depth(topology, depth, k); if (!obj_core) continue; int cpu_count_core = hwloc_bitmap_weight(obj_core->cpuset); if (cpu_count_core == -1) continue; ``` --- #### **Error: Incorrect second argument to `rte_topo_get_nth_lcore_from_domain()` in `get_same_l1_domains()` (test_ring_perf.c and test_stack_perf.c)** In both `app/test/test_ring_perf.c:290` and `app/test/test_stack_perf.c:258`, the function `get_same_l1_domains()` calls: ```c id2 = rte_topo_get_nth_lcore_from_domain(domain, 0, 0, RTE_TOPO_DOMAIN_L1); ``` The second argument (`lcore_pos`) is `0`, which is the same as for `id1`. This will assign **the same lcore** to both `id1` and `id2`, causing the subsequent check `if (id1 == id2) return 3;` to always trigger. This is a logic error: the intent is clearly to get two **different** lcores from the same domain. **Location:** `app/test/test_ring_perf.c:287-290` and `app/test/test_stack_perf.c:255-258` **Fix:** Use position `1` for the second lcore: ```c id1 = rte_topo_get_nth_lcore_from_domain(domain, 0, 0, RTE_TOPO_DOMAIN_L1); id2 = rte_topo_get_nth_lcore_from_domain(domain, 1, 0, RTE_TOPO_DOMAIN_L1); ``` --- #### **Error: Iteration condition in `test_main_lcore_in_domain()` uses wrong domain type for lookup** In `app/test/test_topology.c:211`, the loop iterates over `domain_count` for `domain_types[d]`, but the call to `rte_topo_is_main_lcore_in_domain()` uses `RTE_TOPO_DOMAIN_NUMA` instead of `domain_types[d]`. This means the test only checks the NUMA domain regardless of which domain type `d` selects (L1/L2/L3/L4). **Location:** `app/test/test_topology.c:206-216` ```c for (unsigned int d = 0; d < RTE_DIM(domain_types); d++) { bool main_lcore_found = false; unsigned int domain_count = rte_topo_get_domain_count(domain_types[d]); for (unsigned int dmn_idx = 0; dmn_idx < domain_count; dmn_idx++) { main_lcore_found = rte_topo_is_main_lcore_in_domain(RTE_TOPO_DOMAIN_NUMA, /* BUG: should be domain_types[d] */ dmn_idx); if (main_lcore_found) break; } ``` **Fix:** ```c main_lcore_found = rte_topo_is_main_lcore_in_domain(domain_types[d], dmn_idx); ``` --- #### **Error: Infinite loop risk in `rte_topo_get_nth_lcore_from_domain()` when `ptr->core_count` is 0** In `lib/eal/common/eal_topology.c:296-318`, the function enters a `while (1)` loop that increments `new_lcore_pos`. If `ptr->core_count` is 0 (which the code checks earlier but does not return immediately), the loop will wrap `new_lcore_pos` back to 0 indefinitely, never breaking. While the function returns `RTE_MAX_LCORE` if `ptr->core_count == 0` before the loop, the logic flow is unclear and the loop body does not have a clear termination condition if the core count is 0. **Location:** `lib/eal/common/eal_topology.c:283-318` **Fix:** Add a sanity check inside the loop to prevent infinite iteration: ```c unsigned int iterations = 0; while (1) { if (iterations++ > ptr->core_count * 2) /* safety limit */ return RTE_MAX_LCORE; /* ... rest of loop ... */ } ``` However, the real issue is that the code already returns `RTE_MAX_LCORE` if `ptr->core_count == 0` on line 287, so this is more of a defensive-programming note. The function should be refactored for clarity. --- #### **Error: Missing NULL check after `get_domain_lcore_mapping()` in `rte_topo_get_next_lcore()`** In `rte_topo_get_next_lcore()`, the code calls `get_domain_lcore_mapping(flag, lcore_domain)` and checks if `ptr` is NULL on line 350. However, if `ptr` is NULL, the function returns `RTE_MAX_LCORE`. This is correct, but the subsequent logic on line 381 calls `rte_topo_is_main_lcore_in_domain(flag, lcore_domain)`, which internally may call `get_domain_lcore_mapping()` again. If that call also returns NULL (which it will if the domain is invalid), the function `rte_topo_is_main_lcore_in_domain()` will return `false`, which is safe. However, the logic is fragile and should explicitly handle the NULL case to avoid relying on transitive safety. **Location:** `lib/eal/common/eal_topology.c:381` **Recommendation:** The code is technically safe but could be clearer. No change required, but consider restructuring for maintainability. --- ### Patch 2/3: app/test Topology Tests #### **Error: Macro `RTE_TOPO_FOREACH_WORKER_LCORE_IN_DOMAIN` declares variable in macro expansion (shadowing risk)** In `lib/eal/include/rte_topology.h:243-248`, the macro `RTE_TOPO_FOREACH_WORKER_LCORE_IN_DOMAIN` declares a local variable `main_lcore` inside the macro expansion: ```c #define RTE_TOPO_FOREACH_WORKER_LCORE_IN_DOMAIN(lcore, domain_indx, flag) \ lcore = rte_topo_get_nth_lcore_from_domain(domain, 0, 0, flag); \ uint16_t main_lcore = rte_get_main_lcore(); \ for (lcore = (lcore != main_lcore) ? \ lcore : rte_topo_get_next_lcore(lcore, 1, 0, flag); \ lcore < RTE_MAX_LCORE; \ lcore = rte_topo_get_next_lcore(lcore, 1, 0, flag)) ``` This can cause a compiler error or shadowing if the caller already has a variable named `main_lcore` in scope. Additionally, the macro uses `domain` (line 244) but the parameter is `domain_indx`, which is a typo and will cause a compilation error. **Location:** `lib/eal/include/rte_topology.h:243-248` **Fix:** Wrap in a `do { } while (0)` and use a uniquely-named variable, or document that the macro must not be used if `main_lcore` is already declared. Also fix the typo: ```c #define RTE_TOPO_FOREACH_WORKER_LCORE_IN_DOMAIN(lcore, domain_indx, flag) \ lcore = rte_topo_get_nth_lcore_from_domain(domain_indx, 0, 0, flag); \ uint16_t __topo_main_lcore = rte_get_main_lcore(); \ for (lcore = (lcore != __topo_main_lcore) ? \ lcore : rte_topo_get_next_lcore(lcore, 1, 0, flag); \ lcore < RTE_MAX_LCORE; \ lcore = rte_topo_get_next_lcore(lcore, 1, 0, flag)) ``` --- ### Summary of Correctness Bugs 1. **hwloc topology leak** on `eal_topology_map_layer()` failure 2. **Resource leak** in `eal_topology_map_layer()` on partial allocation failure 3. **NULL pointer dereference** in `eal_topology_map_layer()` inner loop 4. **Logic error** in `get_same_l1_domains()` (same lcore assigned to `id1` and `id2`) 5. **Wrong domain type** in `test_main_lcore_in_domain()` (uses `RTE_TOPO_DOMAIN_NUMA` instead of `domain_types[d]`) 6. **Macro typo** in `RTE_TOPO_FOREACH_WORKER_LCORE_IN_DOMAIN` (uses `domain` instead of `domain_indx`) 7. **Potential infinite loop** in `rte_topo_get_nth_lcore_from_domain()` if `ptr->core_count == 0` (mitigated by early
