NVTX API for Compute Sanitizer Reference Manual
NVTX API for Compute Sanitizer Reference Manual
The reference manual on NVTX API for Compute Sanitizer.
Introduction
Overview
The NVTX Memory API for Compute Sanitizer allows CUDA programs to notify Compute Sanitizer about memory restrictions: memory pools management or permissions restrictions, in addition to memory labeling. The tools are notified through NVTX (NVIDIA Tools Extension), a header-only C library used by various NVIDIA tools. Latest NVTX headers can be downloaded on our GitHub repository (experimental branch).
This API has the following main goals:
Programs can mark allocations as memory pools, allowing Compute Sanitizer to be aware of which parts of this specific allocation are actually used. When using the Memcheck tool, you are notified if unregistered parts of the pool are accessed by the program, errors that could have been missed otherwise. When using the Initcheck tool, in combination with option
--track-unused-memory yes
, you are not notified for unused memory in non-registered regions, therefore avoiding false positives.Programs can label allocations with meaningful names, allowing you to identify an allocation associated to a specific error by its name (e.g., allocation that is leaking, or unused).
Programs can restrict some allocations to a specific set of permissions (e.g., read-only or write-only) applicable for a specific scope (e.g., CUDA stream, device or whole program). When using the Memcheck tool, violation of these restrictions will result in an error.
Usage
Compatibility and Requirements
The Compute Sanitizer tools require CUDA 11.0 or newer.
The NVTX Memory API is supported by Compute Sanitizer starting CUDA 11.3, using the --nvtx yes
option. Starting CUDA 12.0, this option is enabled by default.
Compute Sanitizer requires the CUDA runtime to be initialized before calling NVTX.
// NVTX calls are not allowed before CUDA runtime initialization.
// Forces CUDA runtime initialization.
cudaFree(0);
// NVTX calls are now allowed.
NVTX structures must be zero-initialized. Examples on this page use C++ empty initializer ({}
). If you are using C, you can use memset
or use the intializer syntax with at least one field (C does not support empty initalizers).
NVTX Domain
All NVTX calls requires you to create a NVTX domain. This can be achieved using nvtxDomainCreateA
.
// Requires <nvtx3/nvToolsExt.h>
auto nvtxDomain = nvtxDomainCreateA("my-domain");
For now, NVTX domains have no specific usage, but will have one in a future Compute Sanitizer version.
Suballocation API
Pools Management
Any allocation created with cudaMalloc
can be registered as a memory pool using nvtxMemHeapRegister
. The following code example allocates 64 bytes and registers the allocation as a memory pool.
// Requires <nvtx3/nvToolsExtMem.h>
// (see https://github.com/NVIDIA/NVTX/tree/dev-mem-api/c/include)
void *ptr;
cudaMalloc(&ptr, 64);
nvtxMemVirtualRangeDesc_t nvtxRangeDesc = {};
nvtxRangeDesc.size = 64;
nvtxRangeDesc.ptr = ptr;
nvtxMemHeapDesc_t nvtxHeapDesc = {};
nvtxHeapDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxHeapDesc.structSize = sizeof(nvtxMemHeapDesc_t);
nvtxHeapDesc.usage = NVTX_MEM_HEAP_USAGE_TYPE_SUB_ALLOCATOR;
nvtxHeapDesc.type = NVTX_MEM_TYPE_VIRTUAL_ADDRESS;
nvtxHeapDesc.typeSpecificDescSize = sizeof(nvtxMemVirtualRangeDesc_t);
nvtxHeapDesc.typeSpecificDesc = &nvtxRangeDesc;
auto nvtxPool = nvtxMemHeapRegister(
nvtxDomain,
&nvtxHeapDesc);
Please note that Compute Sanitizer only supports nvtxMemHeapRegister
with parameters usage = NVTX_MEM_HEAP_USAGE_TYPE_SUB_ALLOCATOR
and type = NVTX_MEM_TYPE_VIRTUAL_ADDRESS
. If you are using the CUDA runtime API, nvtxMemHeapRegister
can be used with allocations created with cuMemAlloc
.
An existing pool can be reset to its initial state using nvtxMemHeapReset
. The following example resets the pool previously allocated.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemHeapReset(nvtxDomain, nvtxPool);
In a similar fashion, a pool can be unregistered using nvtxMemHeapUnregister
. An allocation cannot be used after it is unregistered, but the allocation must be freed using cudaFree
to dispose of it.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemHeapUnregister(nvtxDomain, nvtxPool);
For your convenience, calling cudaFree
on a memory pool causes Compute Sanitizer to automatically unregister it.
Suballocations Management
Once a pool is created, users can create suballocations within this pool using nvtxMemRegionsRegister
. For your convenience, you can register multiple regions at the same time. The following example creates a suballocation of 16 bytes at address ptr
. Both ptr
and ptr + 16 bytes
must be part of the pool.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemVirtualRangeDesc_t nvtxRangeDesc = {};
nvtxRangeDesc.size = 16;
nvtxRangeDesc.ptr = ptr;
nvtxMemRegionsRegisterBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemRegionsRegisterBatch_t);
nvtxRegionsDesc.regionType = NVTX_MEM_TYPE_VIRTUAL_ADDRESS;
nvtxRegionsDesc.heap = nvtxPool;
nvtxRegionsDesc.regionCount = 1;
nvtxRegionsDesc.regionDescElementSize = sizeof(nvtxMemVirtualRangeDesc_t);
nvtxRegionsDesc.regionDescElements = &nvtxRangeDesc;
nvtxMemRegionsRegister(nvtxDomain, &nvtxRegionsDesc);
For your convenience, Initcheck assumes that a new suballocation is uninitialized, meaning failure to initialize it might result in error reports. Please note that Compute Sanitizer only supports nvtxMemRegionsRegister
with parameter regionType = NVTX_MEM_TYPE_VIRTUAL_ADDRESS
. Suballocations are considered as regular allocations for NVTX naming and permissions API, therefore it is possible to label them or change their permissions.
Existing suballocations can be resized using nvtxMemRegionsResize
. The following example resizes our previous suballocation at address ptr
from 16 bytes to 32.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemVirtualRangeDesc_t nvtxRangeDesc = {};
nvtxRangeDesc.size = 32;
nvtxRangeDesc.ptr = ptr;
nvtxMemRegionsResizeBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemRegionsResizeBatch_t);
nvtxRegionsDesc.regionType = NVTX_MEM_TYPE_VIRTUAL_ADDRESS;
nvtxRegionsDesc.regionDescCount = 1;
nvtxRegionsDesc.regionDescElementSize = sizeof(nvtxMemVirtualRangeDesc_t);
nvtxRegionsDesc.regionDescElements = &nvtxRangeDesc;
nvtxMemRegionsResize(nvtxDomain, &nvtxRegionsDesc);
In a similar fashion, existing allocations can be removed using nvtxMemRegionsUnregister
. The following example removes our previous suballocation at address ptr
.
nvtxMemRegionRef_t nvtxRegionRef;
nvtxRegionRef.pointer = ptr;
nvtxMemRegionsUnregisterBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemRegionsUnregisterBatch_t);
nvtxRegionsDesc.refType = NVTX_MEM_REGION_REF_TYPE_POINTER;
nvtxRegionsDesc.refCount = 1;
nvtxRegionsDesc.refElementSize = sizeof(nvtxMemRegionRef_t);
nvtxRegionsDesc.refElements = &nvtxRegionRef;
nvtxMemRegionsUnregister(nvtxDomain, &nvtxRegionsDesc);
Omitting to unregister a suballocation is reported as a memory leak if Compute Sanitizer is used in combination with option --leak-check yes
.
Naming API
Any allocation can be assigned a name, so future Compute Sanitizer error reports can refer to an allocation by its name. This example names the allocation at address ptr
: “My Allocation”.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemRegionNameDesc_t nvtxLabelDesc;
nvtxLabelDesc.regionRefType = NVTX_MEM_REGION_REF_TYPE_POINTER;
nvtxLabelDesc.nameType = NVTX_MESSAGE_TYPE_ASCII;
nvtxLabelDesc.region.pointer = ptr;
nvtxLabelDesc.name.ascii = "My Allocation";
nvtxMemRegionsNameBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemRegionsNameBatch_t);
nvtxRegionsDesc.regionCount = 1;
nvtxRegionsDesc.regionElementSize = sizeof(nvtxMemRegionNameDesc_t);
nvtxRegionsDesc.regionElements = &nvtxLabelDesc;
nvtxMemRegionsName(nvtxDomain, &nvtxRegionsDesc);
Please note that Compute Sanitizer only supports nvtxMemRegionsName
with parameter nameType = NVTX_MESSAGE_TYPE_ASCII
for all region elements in regionElements
. As of now, only leak and unused memory reporting features allocation names.
Permissions API
Basic Permissions Management
NVTX Permissions API allows any allocation permissions to be restricted using nvtxMemPermissionsAssign
. For this example, we use the global program scope (by calling nvtxMemCudaGetProcessWidePermissions
), meaning permissions are applied on all kernel launches. This example restricts the allocation at address ptr
to read-only permissions.
// Requires <nvtx3/nvToolsExtMem.h> and <nvtx3/nvToolsExtMemCudaRt.h>
auto processPermHandle = nvtxMemCudaGetProcessWidePermissions(nvtxDomain);
nvtxMemPermissionsAssignRegionDesc_t nvtxPermDesc;
nvtxPermDesc.flags = NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ;
nvtxPermDesc.regionRefType = NVTX_MEM_REGION_REF_TYPE_POINTER;
nvtxPermDesc.region.pointer = ptr;
nvtxMemPermissionsAssignBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemPermissionsAssignBatch_t);
nvtxRegionsDesc.permissions = processPermHandle;
nvtxRegionsDesc.regionCount = 1;
nvtxRegionsDesc.regionElementSize = sizeof(nvtxMemPermissionsAssignRegionDesc_t);
nvtxRegionsDesc.regionElements = &nvtxPermDesc;
nvtxMemPermissionsAssign(nvtxDomain, &nvtxRegionsDesc);
Valid permissions are:
Read:
NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ
Write:
NVTX_MEM_PERMISSIONS_REGION_FLAGS_WRITE
Atomic:
NVTX_MEM_PERMISSIONS_REGION_FLAGS_ATOMIC
A combination of read, write and atomic (using XORs).
Reset:
NVTX_MEM_PERMISSIONS_REGION_FLAGS_RESET
Using special permission NVTX_MEM_PERMISSIONS_REGION_FLAGS_RESET
resets assigned permissions for the specified allocation on the specified scope.
Allocations permissions can be restricted on a per-device basis, using nvtxMemCudaGetDeviceWidePermissions
. The following example gets the permissions handle from device device
, a handle that is used with nvtxMemPermissionsAssign
to change permissions for the allocation at address ptr
, previously restricted to read-only on the global scope, and now read-write for kernel launched on device
(no atomic allowed).
// Requires <nvtx3/nvToolsExtMem.h> and <nvtx3/nvToolsExtMemCudaRt.h>
auto devicePermHandle = nvtxMemCudaGetDeviceWidePermissions(nvtxDomain, device);
nvtxMemPermissionsAssignRegionDesc_t nvtxPermDesc;
nvtxPermDesc.flags = NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ | NVTX_MEM_PERMISSIONS_REGION_FLAGS_WRITE;
nvtxPermDesc.regionRefType = NVTX_MEM_REGION_REF_TYPE_POINTER;
nvtxPermDesc.region.pointer = ptr;
nvtxMemPermissionsAssignBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemPermissionsAssignBatch_t);
nvtxRegionsDesc.permissions = devicePermHandle;
nvtxRegionsDesc.regionCount = 1;
nvtxRegionsDesc.regionElementSize = sizeof(nvtxMemPermissionsAssignRegionDesc_t);
nvtxRegionsDesc.regionElements = &nvtxPermDesc;
nvtxMemPermissionsAssign(nvtxDomain, &nvtxRegionsDesc);
Advanced Permissions Management
Permissions can be assigned to a specific stream scope thanks to custom permissions objects. You can create one using nvtxMemPermissionsCreate
, and bind it to a scope using nvtxMemPermissionsBind
. The following example restricts the allocation at address ptr
to read-only permissions.
// Requires <nvtx3/nvToolsExtMem.h> and <nvtx3/nvToolsExtMemCudaRt.h>
// Create new permissions object.
auto permHandle = nvtxMemPermissionsCreate(nvtxDomain, NVTX_MEM_PERMISSIONS_CREATE_FLAGS_NONE);
nvtxMemPermissionsAssignRegionDesc_t nvtxPermDesc;
nvtxPermDesc.flags = NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ;
nvtxPermDesc.regionRefType = NVTX_MEM_REGION_REF_TYPE_POINTER;
nvtxPermDesc.region.pointer = ptr;
nvtxMemPermissionsAssignBatch_t nvtxRegionsDesc = {};
nvtxRegionsDesc.extCompatID = NVTX_EXT_COMPATID_MEM;
nvtxRegionsDesc.structSize = sizeof(nvtxMemPermissionsAssignBatch_t);
nvtxRegionsDesc.permissions = permHandle;
nvtxRegionsDesc.regionCount = 1;
nvtxRegionsDesc.regionElementSize = sizeof(nvtxMemPermissionsAssignRegionDesc_t);
nvtxRegionsDesc.regionElements = &nvtxPermDesc;
// Assign read-only permissions to allocation at address ptr.
// Permissions will be applied on scope bound to permHandle.
nvtxMemPermissionsAssign(nvtxDomain, &nvtxRegionsDesc);
// Binding will happen on next kernel launch on this CPU thread, meaning the
// stream for this launch will be the one bound to this permissions object.
nvtxMemPermissionsBind(
nvtxDomain,
permHandle,
NVTX_MEM_PERMISSIONS_BIND_SCOPE_CUDA_STREAM,
NVTX_MEM_PERMISSIONS_BIND_FLAGS_NONE);
// permHandle is now bound to stream.
MyKernel<<<BlocksNb, ThreadsNb, 0, stream>>>(ptr);
On permissions object creation or binding, you can specify inheritance restriction flags. For example, excluding write permissions will block access for all allocations with unassigned permissions on that scope. These are applied:
nvtxMemPermissionsCreate
: applied for kernel launches on stream bound to the created object.nvtxMemPermissionsBind
: applied for next kernel launch (on this CPU thread) and others using the same stream.
Please note that Compute Sanitizer only supports nvtxMemPermissionsBind
with parameter scope = NVTX_MEM_PERMISSIONS_BIND_SCOPE_CUDA_STREAM
.
Permissions objects currently bound can be unbound using nvtxMemPermissionsUnbind
and destroyed using nvtxMemPermissionsDestroy
. Permissions object destruction will result in an unbinding.
// Requires <nvtx3/nvToolsExtMem.h>
nvtxMemPermissionsUnbind(nvtxDomain, NVTX_MEM_PERMISSIONS_BIND_SCOPE_CUDA_STREAM)
nvtxMemPermissionsDestroy(nvtxDomain, permHandle);
Please note that Compute Sanitizer only supports nvtxMemPermissionsUnbind
with parameter scope = NVTX_MEM_PERMISSIONS_BIND_SCOPE_CUDA_STREAM
.
Peer devices access can be restricted for all allocations using nvtxMemCudaSetPeerAccess
. If no permissions are set on an active scope for an allocation using nvtxMemPermissionsAssign
, then default permissions set using nvtxMemCudaSetPeerAccess
are applied. The following example restricts accesses to read-only on all devices except device
.
// Requires <nvtx3/nvToolsExtMem.h>
auto permHandle = nvtxMemCudaGetDeviceWidePermissions(nvtxDomain, device);
nvtxMemCudaSetPeerAccess(
nvtxDomain,
permHandle,
NVTX_MEM_CUDA_PEER_ALL_DEVICES,
NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ);
nvtxMemCudaSetPeerAccess(
nvtxDomain,
permHandle,
device,
NVTX_MEM_PERMISSIONS_REGION_FLAGS_READ | NVTX_MEM_PERMISSIONS_REGION_FLAGS_WRITE | NVTX_MEM_PERMISSIONS_REGION_FLAGS_ATOMIC);
Limitations
Please note the Compute Sanitizer support for NVTX Memory API has the following limitations:
Allocation names are visible on leak and unused memory reports, but not on other error reports for now.
Allocation names must be encoded in ASCII, contain only printable characters, and contain between 1 and 49 characters (must comply to the following regex:
^[:print:]{1,49}$
)Permissions are only applied to kernel launches. Other operations, such as
cudaMemcpy
orcudaMemset
, are not supported for now.
Notices
Notice
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