Repository: pytorch
Issue: caching_allocator_delete does not free up the memory allocated by caching_allocator_alloc
Labels: triaged,module: CUDACachingAllocator

### 🐛 Describe the bug

I run the following code in a notebook:

```
import torch
import time

# Reserve 2G GPU RAM
mem_ptr = torch.cuda.caching_allocator_alloc(1024*1024*1024 * 2)

# Sleep 5s
time.sleep(5)

# Free the memory
torch.cuda.caching_allocator_delete(mem_ptr)
```

Then use nvitop to monitor GPU utilization.

I do see that 2165MiB was allocated initially but the memory is still allocated after 5s and freed up only after I restart my notebook kernel.

### Versions

python collect_env.py 
Collecting environment information...
PyTorch version: 2.3.1+cu121
Is debug build: False
CUDA used to build PyTorch: 12.1
ROCM used to build PyTorch: N/A

OS: Ubuntu 24.04 LTS (x86_64)
GCC version: (Ubuntu 13.2.0-23ubuntu4) 13.2.0
Clang version: Could not collect
CMake version: Could not collect
Libc version: glibc-2.39

Python version: 3.12.3 (main, Apr 10 2024, 05:33:47) [GCC 13.2.0] (64-bit runtime)
Python platform: Linux-6.8.0-36-generic-x86_64-with-glibc2.39
Is CUDA available: True
CUDA runtime version: Could not collect
CUDA_MODULE_LOADING set to: LAZY
GPU models and configuration: GPU 0: NVIDIA GeForce GTX 1660 SUPER
Nvidia driver version: 555.42.02
cuDNN version: Probably one of the following:
/usr/lib/x86_64-linux-gnu/libcudnn.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_adv.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_cnn.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_precompiled.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_engines_runtime_compiled.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_graph.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_heuristic.so.9.2.0
/usr/lib/x86_64-linux-gnu/libcudnn_ops.so.9.2.0
HIP runtime version: N/A
MIOpen runtime version: N/A
Is XNNPACK available: True

CPU:
Architecture:                         x86_64
CPU op-mode(s):                       32-bit, 64-bit
Address sizes:                        39 bits physical, 48 bits virtual
Byte Order:                           Little Endian
CPU(s):                               6
On-line CPU(s) list:                  0-5
Vendor ID:                            GenuineIntel
Model name:                           Intel(R) Core(TM) i5-9400 CPU @ 2.90GHz
CPU family:                           6
Model:                                158
Thread(s) per core:                   1
Core(s) per socket:                   6
Socket(s):                            1
Stepping:                             13
CPU(s) scaling MHz:                   20%
CPU max MHz:                          4100.0000
CPU min MHz:                          800.0000
BogoMIPS:                             5799.77
Flags:                                fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc art arch_perfmon pebs bts rep_good nopl xtopology nonstop_tsc cpuid aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx est tm2 ssse3 sdbg fma cx16 xtpr pdcm pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand lahf_lm abm 3dnowprefetch cpuid_fault ssbd ibrs ibpb stibp ibrs_enhanced tpr_shadow flexpriority ept vpid ept_ad fsgsbase tsc_adjust bmi1 avx2 smep bmi2 erms invpcid mpx rdseed adx smap clflushopt intel_pt xsaveopt xsavec xgetbv1 xsaves dtherm ida arat pln pts hwp hwp_notify hwp_act_window hwp_epp vnmi md_clear flush_l1d arch_capabilities
Virtualization:                       VT-x
L1d cache:                            192 KiB (6 instances)
L1i cache:                            192 KiB (6 instances)
L2 cache:                             1.5 MiB (6 instances)
L3 cache:                             9 MiB (1 instance)
NUMA node(s):                         1
NUMA node0 CPU(s):                    0-5
Vulnerability Gather data sampling:   Mitigation; Microcode
Vulnerability Itlb multihit:          KVM: Mitigation: VMX disabled
Vulnerability L1tf:                   Not affected
Vulnerability Mds:                    Not affected
Vulnerability Meltdown:               Not affected
Vulnerability Mmio stale data:        Mitigation; Clear CPU buffers; SMT disabled
Vulnerability Reg file data sampling: Not affected
Vulnerability Retbleed:               Mitigation; Enhanced IBRS
Vulnerability Spec rstack overflow:   Not affected
Vulnerability Spec store bypass:      Mitigation; Speculative Store Bypass disabled via prctl
Vulnerability Spectre v1:             Mitigation; usercopy/swapgs barriers and __user pointer sanitization
Vulnerability Spectre v2:             Mitigation; Enhanced / Automatic IBRS; IBPB conditional; RSB filling; PBRSB-eIBRS SW sequence; BHI Syscall hardening, KVM SW loop
Vulnerability Srbds:                  Mitigation; Microcode
Vulnerability Tsx async abort:        Not affected

Versions of relevant libraries:
[pip3] mypy-extensions==1.0.0
[pip3] numpy==1.26.4
[pip3] optree==0.11.0
[pip3] torch==2.3.1
[pip3] torchaudio==2.3.1
[pip3] torchvision==0.18.1
[conda] Could not collect