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8299030: Refactor ReservedSpace::reserve

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Reviewed-by: dholmes, tschatzl
This commit is contained in:
Albert Mingkun Yang 2023-01-02 14:59:11 +00:00
parent ce6395a135
commit 67086ebf80
1 changed files with 16 additions and 18 deletions

34
src/hotspot/share/memory/virtualspace.cpp

@ -223,12 +223,13 @@ void ReservedSpace::reserve(size_t size,
assert(is_aligned(size, alignment), "Size must be aligned to the requested alignment");
// There are basically three different cases that we need to handle below:
// - Mapping backed by a file
// - Mapping backed by explicit large pages
// - Mapping backed by normal pages or transparent huge pages
// 1. Mapping backed by a file
// 2. Mapping backed by explicit large pages
// 3. Mapping backed by normal pages or transparent huge pages
// The first two have restrictions that requires the whole mapping to be
// committed up front. To record this the ReservedSpace is marked 'special'.
// == Case 1 ==
if (_fd_for_heap != -1) {
// When there is a backing file directory for this space then whether
// large pages are allocated is up to the filesystem of the backing file.
@ -239,34 +240,31 @@ void ReservedSpace::reserve(size_t size,
}
// Always return, not possible to fall back to reservation not using a file.
return;
} else if (use_explicit_large_pages(page_size)) {
}
// == Case 2 ==
if (use_explicit_large_pages(page_size)) {
// System can't commit large pages i.e. use transparent huge pages and
// the caller requested large pages. To satisfy this request we use
// explicit large pages and these have to be committed up front to ensure
// no reservations are lost.
size_t used_page_size = page_size;
char* base = NULL;
do {
base = reserve_memory_special(requested_address, size, alignment, used_page_size, executable);
char* base = reserve_memory_special(requested_address, size, alignment, page_size, executable);
if (base != NULL) {
break;
// Successful reservation using large pages.
initialize_members(base, size, alignment, page_size, true, executable);
return;
}
used_page_size = os::page_sizes().next_smaller(used_page_size);
} while (used_page_size > (size_t) os::vm_page_size());
page_size = os::page_sizes().next_smaller(page_size);
} while (page_size > (size_t) os::vm_page_size());
if (base != NULL) {
// Successful reservation using large pages.
initialize_members(base, size, alignment, used_page_size, true, executable);
return;
}
// Failed to reserve explicit large pages, do proper logging.
log_on_large_pages_failure(requested_address, size);
// Now fall back to normal reservation.
page_size = os::vm_page_size();
assert(page_size == (size_t) os::vm_page_size(), "inv");
}
// Not a 'special' reservation.
// == Case 3 ==
char* base = reserve_memory(requested_address, size, alignment, -1, executable);
if (base != NULL) {
// Successful mapping.