tools/memleak: Use compact size of key for sizes and memptrs maps

As sizes and memptrs map are to store the temporal information of each thread,
use only tid portion of the return value of bpf_get_current_pid_tgid as a key
of sizes and memptrs map. This change could reduce the key size of each map
from 64 bits to 32 bits. The lower 32 bits portion of the return value of
bpf_get_current_pid_tgid is kernel's view of the pid, which in user space is
usually presented as the tid.

Please refer this document for further information:
https://github.com/iovisor/bcc/blob/master/docs/reference_guide.md#4-bpf_get_current_pid_tgid

tools/memleak.py

@@ -161,9 +161,9 @@ def run_command_get_pid(command):
  u64 number_of_allocs;
 };
 
-BPF_HASH(sizes, u64);
+BPF_HASH(sizes, u32, u64);
 BPF_HASH(allocs, u64, struct alloc_info_t, 1000000);
-BPF_HASH(memptrs, u64, u64);
+BPF_HASH(memptrs, u32, u64);
 BPF_STACK_TRACE(stack_traces, 10240);
 BPF_HASH(combined_allocs, u64, struct combined_alloc_info_t, 10240);
 
@@ -208,25 +208,25 @@ def run_command_get_pid(command):
  return 0;
  }
 
- u64 pid = bpf_get_current_pid_tgid();
+ u32 tid = bpf_get_current_pid_tgid();
  u64 size64 = size;
- sizes.update(&pid, &size64);
+ sizes.update(&tid, &size64);
 
  if (SHOULD_PRINT)
  bpf_trace_printk("alloc entered, size = %u\\n", size);
  return 0;
 }
 
 static inline int gen_alloc_exit2(struct pt_regs *ctx, u64 address) {
- u64 pid = bpf_get_current_pid_tgid();
- u64* size64 = sizes.lookup(&pid);
+ u32 tid = bpf_get_current_pid_tgid();
+ u64* size64 = sizes.lookup(&tid);
  struct alloc_info_t info = {0};
 
  if (size64 == 0)
  return 0; // missed alloc entry
 
  info.size = *size64;
- sizes.delete(&pid);
+ sizes.delete(&tid);
 
  if (address != 0) {
  info.timestamp_ns = bpf_ktime_get_ns();
@@ -307,21 +307,21 @@ def run_command_get_pid(command):
 int posix_memalign_enter(struct pt_regs *ctx, void **memptr, size_t alignment,
  size_t size) {
  u64 memptr64 = (u64)(size_t)memptr;
- u64 pid = bpf_get_current_pid_tgid();
+ u32 tid = bpf_get_current_pid_tgid();
 
- memptrs.update(&pid, &memptr64);
+ memptrs.update(&tid, &memptr64);
  return gen_alloc_enter(ctx, size);
 }
 
 int posix_memalign_exit(struct pt_regs *ctx) {
- u64 pid = bpf_get_current_pid_tgid();
- u64 *memptr64 = memptrs.lookup(&pid);
+ u32 tid = bpf_get_current_pid_tgid();
+ u64 *memptr64 = memptrs.lookup(&tid);
  void *addr;
 
  if (memptr64 == 0)
  return 0;
 
- memptrs.delete(&pid);
+ memptrs.delete(&tid);
 
  if (bpf_probe_read_user(&addr, sizeof(void*), (void*)(size_t)*memptr64))
  return 0;