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src: simplify large pages mapping code #32396

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src: simplify large pages mapping code #32396

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81 changes: 25 additions & 56 deletions src/large_pages/node_large_page.cc
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Expand Up @@ -339,20 +339,23 @@ __attribute__((__noinline__))
MoveTextRegionToLargePages(const text_region& r) {
void* nmem = nullptr;
void* tmem = nullptr;
int ret = 0;

size_t size = r.to - r.from;
void* start = r.from;
size_t size = r.to - r.from;

auto free_mems = OnScopeLeave([&nmem, &tmem, size]() {
if (nmem != nullptr && nmem != MAP_FAILED && munmap(nmem, size) == -1)
PrintSystemError(errno);
if (tmem != nullptr && tmem != MAP_FAILED && munmap(tmem, size) == -1)
PrintSystemError(errno);
Comment on lines +346 to +349
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Suggested change
if (nmem != nullptr && nmem != MAP_FAILED && munmap(nmem, size) == -1)
PrintSystemError(errno);
if (tmem != nullptr && tmem != MAP_FAILED && munmap(tmem, size) == -1)
PrintSystemError(errno);
if ((nmem != nullptr && nmem != MAP_FAILED && munmap(nmem, size) == -1) ||
(tmem != nullptr && tmem != MAP_FAILED && munmap(tmem, size) == -1)) {
PrintSystemError(errno);
}

Alternatively, it may be a bit cleaner to use a custom smart pointer with a deleter for these...

e.g. bit more verbose...

  struct Mmap {
    void* mem = nullptr;
    size_t size = 0;
    Mmap(void* start, size_t size, int prot, int flags) {
      mem = mmap(start, size, prot, flags, -1, 0);
    }
  };
  struct MmapDeleter {
    void operator()(Mmap* ptr) const noexcept {
      if (ptr.mem != nullptr &&
          ptr.mem != MAP_FAILED &&
          munmap(ptr.mem, ptr.size) == -1)
        PrintSystemError(errno); 
    }
  };
  using MmapPointer = std::unique_ptr<Mmap, MmapDeleter>;

then...

  MmapPointer nmem;
  MmapPointer tmem;

  // ...
  size_t size = r.to - r.from; 

  // ...
  nmem = std::make_unique(nullptr, size,
                          PROT_READ | PROT_WRITE,
                          MAP_PRIVATE | MAP_ANONYMOUS);
  if (nmem.mem == MAP_FAILED)
    goto fail;

  // ...
  tmem = std::make_unique(start, size,
                          PROT_READ | PROT_WRITE,
                          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED);
  if (tmem.mem == MAP_FAILED)
    goto fail;

});

// Allocate temporary region preparing for copy.
#if !defined (__FreeBSD__)
// Allocate temporary region and back up the code we will re-map.
nmem = mmap(nullptr, size,
PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (nmem == MAP_FAILED) {
PrintSystemError(errno);
return -1;
}

if (nmem == MAP_FAILED) goto fail;
memcpy(nmem, r.from, size);
#endif

#if defined(__linux__)
// We already know the original page is r-xp
Expand All @@ -362,32 +365,15 @@ MoveTextRegionToLargePages(const text_region& r) {
tmem = mmap(start, size,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1 , 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
return -1;
}

ret = madvise(tmem, size, 14 /* MADV_HUGEPAGE */);
if (ret == -1) {
PrintSystemError(errno);
ret = munmap(tmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return -1;
}
if (tmem == MAP_FAILED) goto fail;
if (madvise(tmem, size, 14 /* MADV_HUGEPAGE */) == -1) goto fail;
memcpy(start, nmem, size);
#elif defined(__FreeBSD__)
tmem = mmap(start, size,
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED |
MAP_ALIGNED_SUPER, -1 , 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return -1;
}
if (tmem == MAP_FAILED) goto fail;
#elif defined(__APPLE__)
// There is not enough room to reserve the mapping close
// to the region address so we content to give a hint
Expand All @@ -398,37 +384,20 @@ MoveTextRegionToLargePages(const text_region& r) {
PROT_READ | PROT_WRITE | PROT_EXEC,
MAP_PRIVATE | MAP_ANONYMOUS,
VM_FLAGS_SUPERPAGE_SIZE_2MB, 0);
if (tmem == MAP_FAILED) {
PrintSystemError(errno);
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return -1;
}
if (tmem == MAP_FAILED) goto fail;
memcpy(tmem, nmem, size);
ret = mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC);
if (ret == -1) {
PrintSystemError(errno);
ret = munmap(tmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return -1;
}
if (mprotect(start, size, PROT_READ | PROT_WRITE | PROT_EXEC) == -1)
goto fail;
memcpy(start, tmem, size);
#endif

ret = mprotect(start, size, PROT_READ | PROT_EXEC);
if (ret == -1) {
PrintSystemError(errno);
ret = munmap(tmem, size);
if (ret == -1) {
PrintSystemError(errno);
}
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return -1;
}
if (-1 == munmap(nmem, size)) PrintSystemError(errno);
return ret;
if (mprotect(start, size, PROT_READ | PROT_EXEC) == -1) goto fail;
// We need not `munmap(tmem, size)` in the above `OnScopeLeave` on success.
tmem = nullptr;
return 0;
fail:
PrintSystemError(errno);
return -1;
}
#endif // defined(NODE_ENABLE_LARGE_CODE_PAGES) && NODE_ENABLE_LARGE_CODE_PAGES

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