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8224871: os::attempt_reserve_memory_at() tries too hard

Browse source 
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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48
src/hotspot/os/bsd/os_bsd.cpp
View file

@ -2189,11 +2189,6 @@ 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,
@ -2216,51 +2211,8 @@ 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.
size_t top_overlap = requested_addr + (bytes + gap) - base[i];
if (top_overlap >= 0 && top_overlap < bytes) {
unmap_memory(base[i], top_overlap);
base[i] += top_overlap;
size[i] = bytes - top_overlap;
} else {
size_t bottom_overlap = base[i] + bytes - requested_addr;
if (bottom_overlap >= 0 && 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;
}
}
// Sleep forever; naked call to OS-specific sleep; use with CAUTION
void os::infinite_sleep() {

48
src/hotspot/os/linux/os_linux.cpp
View file

@ -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,
@ -4132,51 +4127,8 @@ 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;
}
}
// Sleep forever; naked call to OS-specific sleep; use with CAUTION
void os::infinite_sleep() {

106
src/hotspot/os/solaris/os_solaris.cpp
View file

@ -2553,17 +2553,6 @@ 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];
// Solaris adds a gap between mmap'ed regions. The size of the gap
// is dependent on the requested size and the MMU. Our initial gap
// value here is just a guess and will be corrected later.
bool had_top_overlap = false;
bool have_adjusted_gap = false;
size_t gap = 0x400000;
// 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,
@ -2572,105 +2561,18 @@ char* os::pd_attempt_reserve_memory_at(size_t bytes, char* requested_addr) {
assert(bytes % os::vm_page_size() == 0, "reserving unexpected size block");
// Since snv_84, Solaris attempts to honor the address hint - see 5003415.
// Give it a try, if the kernel honors the hint we can return immediately.
char* addr = Solaris::anon_mmap(requested_addr, bytes, 0, false);
volatile int err = errno;
if (addr == requested_addr) {
return addr;
} else if (addr != NULL) {
}
if (addr != NULL) {
pd_unmap_memory(addr, bytes);
}
if (log_is_enabled(Warning, os)) {
char buf[256];
buf[0] = '\0';
if (addr == NULL) {
jio_snprintf(buf, sizeof(buf), ": %s", os::strerror(err));
}
log_info(os)("attempt_reserve_memory_at: couldn't reserve " SIZE_FORMAT " bytes at "
PTR_FORMAT ": reserve_memory_helper returned " PTR_FORMAT
"%s", bytes, requested_addr, addr, buf);
}
// Address hint method didn't work. Fall back to the old method.
// In theory, once SNV becomes our oldest supported platform, this
// code will no longer be needed.
//
// Repeatedly allocate blocks until the block is allocated at the
// right spot. Give up after max_tries.
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;
}
// check that the gap value is right
if (had_top_overlap && !have_adjusted_gap) {
size_t actual_gap = base[i-1] - base[i] - bytes;
if (gap != actual_gap) {
// adjust the gap value and retry the last 2 allocations
assert(i > 0, "gap adjustment code problem");
have_adjusted_gap = true; // adjust the gap only once, just in case
gap = actual_gap;
log_info(os)("attempt_reserve_memory_at: adjusted gap to 0x%lx", gap);
unmap_memory(base[i], bytes);
unmap_memory(base[i-1], size[i-1]);
i-=2;
continue;
}
}
// Does this overlap the block we wanted? Give back the overlapped
// parts and try again.
//
// There is still a bug in this code: if top_overlap == bytes,
// the overlap is offset from requested region by the value of gap.
// In this case giving back the overlapped part will not work,
// because we'll give back the entire block at base[i] and
// therefore the subsequent allocation will not generate a new gap.
// This could be fixed with a new algorithm that used larger
// or variable size chunks to find the requested region -
// but such a change would introduce additional complications.
// It's rare enough that the planets align for this bug,
// so we'll just wait for a fix for 6204603/5003415 which
// will provide a mmap flag to allow us to avoid this business.
size_t top_overlap = requested_addr + (bytes + gap) - base[i];
if (top_overlap >= 0 && top_overlap < bytes) {
had_top_overlap = true;
unmap_memory(base[i], top_overlap);
base[i] += top_overlap;
size[i] = bytes - top_overlap;
} else {
size_t bottom_overlap = base[i] + bytes - requested_addr;
if (bottom_overlap >= 0 && bottom_overlap < bytes) {
if (bottom_overlap == 0) {
log_info(os)("attempt_reserve_memory_at: possible alignment bug");
}
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]);
}
}
return (i < max_tries) ? requested_addr : NULL;
return NULL;
}
bool os::pd_release_memory(char* addr, size_t bytes) {