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8224871: os::attempt_reserve_memory_at() tries too hard

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Reviewed-by: pliden, coleenp, stuefe
This commit is contained in:
Erik Österlund 2019-06-11 10:55:17 +02:00
parent 2f25526470
commit cf79907536
3 changed files with 6 additions and 200 deletions
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50
src/hotspot/os/linux/os_linux.cpp
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@ -4105,11 +4105,6 @@ char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr, int f
// available (and not reserved for something else).
char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
const int max_tries = 10;
char* base[max_tries];
size_t size[max_tries];
const size_t gap = 0x000000;
// Assert only that the size is a multiple of the page size, since
// that's all that mmap requires, and since that's all we really know
// about at this low abstraction level. If we need higher alignment,
@ -4132,50 +4127,7 @@ char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
anon_munmap(addr, bytes);
}
int i;
for (i = 0; i < max_tries; ++i) {
base[i] = reserve_memory(bytes);
if (base[i] != NULL) {
// Is this the block we wanted?
if (base[i] == requested_addr) {
size[i] = bytes;
break;
}
// Does this overlap the block we wanted? Give back the overlapped
// parts and try again.
ptrdiff_t top_overlap = requested_addr + (bytes + gap) - base[i];
if (top_overlap >= 0 && (size_t)top_overlap < bytes) {
unmap_memory(base[i], top_overlap);
base[i] += top_overlap;
size[i] = bytes - top_overlap;
} else {
ptrdiff_t bottom_overlap = base[i] + bytes - requested_addr;
if (bottom_overlap >= 0 && (size_t)bottom_overlap < bytes) {
unmap_memory(requested_addr, bottom_overlap);
size[i] = bytes - bottom_overlap;
} else {
size[i] = bytes;
}
}
}
}
// Give back the unused reserved pieces.
for (int j = 0; j < i; ++j) {
if (base[j] != NULL) {
unmap_memory(base[j], size[j]);
}
}
if (i < max_tries) {
return requested_addr;
} else {
return NULL;
}
return NULL;
}
// Sleep forever; naked call to OS-specific sleep; use with CAUTION