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Implement guard pages.

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Adding guarded extents, which are regular extents surrounded by guard pages
(mprotected).  To reduce syscalls, small guarded extents are cached as a
separate eset in ecache, and decay through the dirty / muzzy / retained pipeline
as usual.
This commit is contained in:
Qi Wang 2021-04-26 14:22:25 -07:00 • committed by Qi Wang
parent 7bb05e04be
commit deb8e62a83
41 changed files with 920 additions and 251 deletions
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47
src/pages.c
View file

@ -316,14 +316,10 @@ pages_unmap(void *addr, size_t size) {
}
static bool
pages_commit_impl(void *addr, size_t size, bool commit) {
os_pages_commit(void *addr, size_t size, bool commit) {
assert(PAGE_ADDR2BASE(addr) == addr);
assert(PAGE_CEILING(size) == size);
if (os_overcommits) {
return true;
}
#ifdef _WIN32
return (commit ? (addr != VirtualAlloc(addr, size, MEM_COMMIT,
PAGE_READWRITE)) : (!VirtualFree(addr, size, MEM_DECOMMIT)));
@ -348,6 +344,15 @@ pages_commit_impl(void *addr, size_t size, bool commit) {
#endif
}
static bool
pages_commit_impl(void *addr, size_t size, bool commit) {
if (os_overcommits) {
return true;
}
return os_pages_commit(addr, size, commit);
}
bool
pages_commit(void *addr, size_t size) {
return pages_commit_impl(addr, size, true);
@ -358,6 +363,38 @@ pages_decommit(void *addr, size_t size) {
return pages_commit_impl(addr, size, false);
}
void
pages_mark_guards(void *head, void *tail) {
assert(head != NULL && tail != NULL);
assert((uintptr_t)head < (uintptr_t)tail);
#ifdef JEMALLOC_HAVE_MPROTECT
mprotect(head, PAGE, PROT_NONE);
mprotect(tail, PAGE, PROT_NONE);
#else
/* Decommit sets to PROT_NONE / MEM_DECOMMIT. */
os_pages_commit(head, PAGE, false);
os_pages_commit(tail, PAGE, false);
#endif
}
void
pages_unmark_guards(void *head, void *tail) {
assert(head != NULL && tail != NULL);
assert((uintptr_t)head < (uintptr_t)tail);
#ifdef JEMALLOC_HAVE_MPROTECT
size_t range = (uintptr_t)tail - (uintptr_t)head + PAGE;
if (range <= SC_LARGE_MINCLASS) {
mprotect(head, range, PROT_READ | PROT_WRITE);
} else {
mprotect(head, PAGE, PROT_READ | PROT_WRITE);
mprotect(tail, PAGE, PROT_READ | PROT_WRITE);
}
#else
os_pages_commit(head, PAGE, true);
os_pages_commit(tail, PAGE, true);
#endif
}
bool
pages_purge_lazy(void *addr, size_t size) {
assert(ALIGNMENT_ADDR2BASE(addr, os_page) == addr);