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8273872: ZGC: Explicitly use 2M large pages

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Reviewed-by: eosterlund, tschatzl, stefank
This commit is contained in:
Per Liden 2021-09-17 07:51:45 +00:00
parent 54b456764b
commit 1890d85c0e
2 changed files with 16 additions and 9 deletions
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18
src/hotspot/os/linux/gc/z/zPhysicalMemoryBacking_linux.cpp
View File

@ -58,6 +58,9 @@
#ifndef MFD_HUGETLB
#define MFD_HUGETLB 0x0004U
#endif
#ifndef MFD_HUGE_2MB
#define MFD_HUGE_2MB 0x54000000U
#endif
// open(2) flags
#ifndef O_CLOEXEC
@ -175,12 +178,6 @@ ZPhysicalMemoryBacking::ZPhysicalMemoryBacking(size_t max_capacity) :
return;
}
if (ZLargePages::is_explicit() && os::large_page_size() != ZGranuleSize) {
log_error_p(gc)("Incompatible large page size configured " SIZE_FORMAT " (expected " SIZE_FORMAT ")",
os::large_page_size(), ZGranuleSize);
return;
}
// Make sure the filesystem block size is compatible
if (ZGranuleSize % _block_size != 0) {
log_error_p(gc)("Filesystem backing the heap has incompatible block size (" SIZE_FORMAT ")",
@ -199,17 +196,20 @@ ZPhysicalMemoryBacking::ZPhysicalMemoryBacking(size_t max_capacity) :
}
int ZPhysicalMemoryBacking::create_mem_fd(const char* name) const {
assert(ZGranuleSize == 2 * M, "Granule size must match MFD_HUGE_2MB");
// Create file name
char filename[PATH_MAX];
snprintf(filename, sizeof(filename), "%s%s", name, ZLargePages::is_explicit() ? ".hugetlb" : "");
// Create file
const int extra_flags = ZLargePages::is_explicit() ? MFD_HUGETLB : 0;
const int extra_flags = ZLargePages::is_explicit() ? (MFD_HUGETLB | MFD_HUGE_2MB) : 0;
const int fd = ZSyscall::memfd_create(filename, MFD_CLOEXEC | extra_flags);
if (fd == -1) {
ZErrno err;
log_debug_p(gc, init)("Failed to create memfd file (%s)",
((ZLargePages::is_explicit() && err == EINVAL) ? "Hugepages not supported" : err.to_string()));
(ZLargePages::is_explicit() && (err == EINVAL || err == ENODEV)) ?
"Hugepages (2M) not available" : err.to_string());
return -1;
}
@ -445,7 +445,7 @@ ZErrno ZPhysicalMemoryBacking::fallocate_compat_mmap_tmpfs(size_t offset, size_t
}
// Advise mapping to use transparent huge pages
os::realign_memory((char*)addr, length, os::large_page_size());
os::realign_memory((char*)addr, length, ZGranuleSize);
// Touch the mapping (safely) to make sure it's backed by memory
const bool backed = safe_touch_mapping(addr, length, _block_size);

7
src/hotspot/share/gc/z/zArguments.cpp
View File

@ -72,6 +72,13 @@ void ZArguments::initialize() {
vm_exit_during_initialization("The flag -XX:+UseZGC can not be combined with -XX:ConcGCThreads=0");
}
// Large page size must match granule size
if (!FLAG_IS_DEFAULT(LargePageSizeInBytes) && LargePageSizeInBytes != ZGranuleSize) {
vm_exit_during_initialization(err_msg("Incompatible -XX:LargePageSizeInBytes, only "
SIZE_FORMAT "M large pages are supported by ZGC",
ZGranuleSize / M));
}
// The heuristics used when UseDynamicNumberOfGCThreads is
// enabled defaults to using a ZAllocationSpikeTolerance of 1.
if (UseDynamicNumberOfGCThreads && FLAG_IS_DEFAULT(ZAllocationSpikeTolerance)) {