340 lines
12 KiB
C
340 lines
12 KiB
C
#ifndef JEMALLOC_INTERNAL_EHOOKS_H
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#define JEMALLOC_INTERNAL_EHOOKS_H
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/*
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* This module is the internal interface to the extent hooks (both
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* user-specified and external). Eventually, this will give us the flexibility
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* to use multiple different versions of user-visible extent-hook APIs under a
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* single user interface.
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*/
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#include "jemalloc/internal/atomic.h"
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extern const extent_hooks_t ehooks_default_extent_hooks;
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typedef struct ehooks_s ehooks_t;
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struct ehooks_s {
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/* Logically an extent_hooks_t *. */
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atomic_p_t ptr;
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};
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extern const extent_hooks_t ehooks_default_extent_hooks;
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/*
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* These are not really part of the public API. Each hook has a fast-path for
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* the default-hooks case that can avoid various small inefficiencies:
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* - Forgetting tsd and then calling tsd_get within the hook.
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* - Getting more state than necessary out of the extent_t.
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* - Doing arena_ind -> arena -> arena_ind lookups.
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* By making the calls to these functions visible to the compiler, it can move
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* those extra bits of computation down below the fast-paths where they get ignored.
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*/
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void *ehooks_default_alloc_impl(tsdn_t *tsdn, void *new_addr, size_t size,
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size_t alignment, bool *zero, bool *commit, unsigned arena_ind);
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bool ehooks_default_dalloc_impl(void *addr, size_t size);
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void ehooks_default_destroy_impl(void *addr, size_t size);
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bool ehooks_default_commit_impl(void *addr, size_t offset, size_t length);
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bool ehooks_default_decommit_impl(void *addr, size_t offset, size_t length);
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#ifdef PAGES_CAN_PURGE_LAZY
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bool ehooks_default_purge_lazy_impl(void *addr, size_t offset, size_t length);
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#endif
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#ifdef PAGES_CAN_PURGE_FORCED
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bool ehooks_default_purge_forced_impl(void *addr, size_t offset, size_t length);
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#endif
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bool ehooks_default_split_impl();
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bool ehooks_default_merge_impl(void *addr_a, void *addr_b);
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void ehooks_default_zero_impl(void *addr, size_t size);
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/*
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* We don't officially support reentrancy from wtihin the extent hooks. But
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* various people who sit within throwing distance of the jemalloc team want
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* that functionality in certain limited cases. The default reentrancy guards
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* assert that we're not reentrant from a0 (since it's the bootstrap arena,
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* where reentrant allocations would be redirected), which we would incorrectly
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* trigger in cases where a0 has extent hooks (those hooks themselves can't be
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* reentrant, then, but there are reasonable uses for such functionality, like
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* putting internal metadata on hugepages). Therefore, we use the raw
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* reentrancy guards.
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*
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* Eventually, we need to think more carefully about whether and where we
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* support allocating from within extent hooks (and what that means for things
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* like profiling, stats collection, etc.), and document what the guarantee is.
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*/
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static inline void
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ehooks_pre_reentrancy(tsdn_t *tsdn) {
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tsd_t *tsd = tsdn_null(tsdn) ? tsd_fetch() : tsdn_tsd(tsdn);
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tsd_pre_reentrancy_raw(tsd);
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}
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static inline void
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ehooks_post_reentrancy(tsdn_t *tsdn) {
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tsd_t *tsd = tsdn_null(tsdn) ? tsd_fetch() : tsdn_tsd(tsdn);
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tsd_post_reentrancy_raw(tsd);
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}
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/* Beginning of the public API. */
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void ehooks_init(ehooks_t *ehooks, extent_hooks_t *extent_hooks);
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static inline void
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ehooks_set_extent_hooks_ptr(ehooks_t *ehooks, extent_hooks_t *extent_hooks) {
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atomic_store_p(&ehooks->ptr, extent_hooks, ATOMIC_RELEASE);
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}
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static inline extent_hooks_t *
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ehooks_get_extent_hooks_ptr(ehooks_t *ehooks) {
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return (extent_hooks_t *)atomic_load_p(&ehooks->ptr, ATOMIC_ACQUIRE);
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}
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static inline bool
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ehooks_are_default(ehooks_t *ehooks) {
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return ehooks_get_extent_hooks_ptr(ehooks) ==
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&ehooks_default_extent_hooks;
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}
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/*
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* In some cases, a caller needs to allocate resources before attempting to call
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* a hook. If that hook is doomed to fail, this is wasteful. We therefore
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* include some checks for such cases.
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*/
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static inline bool
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ehooks_split_will_fail(ehooks_t *ehooks) {
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return ehooks_get_extent_hooks_ptr(ehooks)->split == NULL;
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}
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static inline bool
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ehooks_merge_will_fail(ehooks_t *ehooks) {
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return ehooks_get_extent_hooks_ptr(ehooks)->merge == NULL;
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}
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/*
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* Some hooks are required to return zeroed memory in certain situations. In
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* debug mode, we do some heuristic checks that they did what they were supposed
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* to.
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*
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* This isn't really ehooks-specific (i.e. anyone can check for zeroed memory).
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* But incorrect zero information indicates an ehook bug.
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*/
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static inline void
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ehooks_debug_zero_check(void *addr, size_t size) {
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assert(((uintptr_t)addr & PAGE_MASK) == 0);
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assert((size & PAGE_MASK) == 0);
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assert(size > 0);
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if (config_debug) {
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/* Check the whole first page. */
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size_t *p = (size_t *)addr;
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for (size_t i = 0; i < PAGE / sizeof(size_t); i++) {
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assert(p[i] == 0);
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}
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/*
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* And 4 spots within. There's a tradeoff here; the larger
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* this number, the more likely it is that we'll catch a bug
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* where ehooks return a sparsely non-zero range. But
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* increasing the number of checks also increases the number of
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* page faults in debug mode. FreeBSD does much of their
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* day-to-day development work in debug mode, so we don't want
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* even the debug builds to be too slow.
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*/
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const size_t nchecks = 4;
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assert(PAGE >= sizeof(size_t) * nchecks);
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for (size_t i = 0; i < nchecks; ++i) {
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assert(p[i * (size / sizeof(size_t) / nchecks)] == 0);
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}
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}
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}
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static inline void *
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ehooks_alloc(tsdn_t *tsdn, ehooks_t *ehooks, void *new_addr, size_t size,
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size_t alignment, bool *zero, bool *commit, unsigned arena_ind) {
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bool orig_zero = *zero;
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void *ret;
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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ret = ehooks_default_alloc_impl(tsdn, new_addr, size,
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alignment, zero, commit, arena_ind);
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} else {
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ehooks_pre_reentrancy(tsdn);
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ret = extent_hooks->alloc(extent_hooks, new_addr, size,
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alignment, zero, commit, arena_ind);
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ehooks_post_reentrancy(tsdn);
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}
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assert(new_addr == NULL || ret == NULL || new_addr == ret);
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assert(!orig_zero || *zero);
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if (*zero && ret != NULL) {
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ehooks_debug_zero_check(ret, size);
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}
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return ret;
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}
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static inline bool
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ehooks_dalloc(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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bool committed, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_dalloc_impl(addr, size);
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} else if (extent_hooks->dalloc == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->dalloc(extent_hooks, addr, size,
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committed, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline void
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ehooks_destroy(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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bool committed, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_destroy_impl(addr, size);
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} else if (extent_hooks->destroy == NULL) {
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return;
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} else {
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ehooks_pre_reentrancy(tsdn);
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extent_hooks->destroy(extent_hooks, addr, size, committed,
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arena_ind);
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ehooks_post_reentrancy(tsdn);
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}
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}
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static inline bool
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ehooks_commit(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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size_t offset, size_t length, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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bool err;
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if (extent_hooks == &ehooks_default_extent_hooks) {
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err = ehooks_default_commit_impl(addr, offset, length);
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} else if (extent_hooks->commit == NULL) {
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err = true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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err = extent_hooks->commit(extent_hooks, addr, size,
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offset, length, arena_ind);
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ehooks_post_reentrancy(tsdn);
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}
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if (!err) {
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ehooks_debug_zero_check(addr, size);
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}
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return err;
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}
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static inline bool
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ehooks_decommit(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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size_t offset, size_t length, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_decommit_impl(addr, offset, length);
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} else if (extent_hooks->decommit == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->decommit(extent_hooks, addr, size,
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offset, length, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline bool
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ehooks_purge_lazy(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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size_t offset, size_t length, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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#ifdef PAGES_CAN_PURGE_LAZY
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_purge_lazy_impl(addr, offset, length);
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}
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#endif
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if (extent_hooks->purge_lazy == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->purge_lazy(extent_hooks, addr, size,
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offset, length, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline bool
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ehooks_purge_forced(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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size_t offset, size_t length, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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/*
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* It would be correct to have a ehooks_debug_zero_check call at the end
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* of this function; purge_forced is required to zero. But checking
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* would touch the page in question, which may have performance
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* consequences (imagine the hooks are using hugepages, with a global
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* zero page off). Even in debug mode, it's usually a good idea to
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* avoid cases that can dramatically increase memory consumption.
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*/
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#ifdef PAGES_CAN_PURGE_FORCED
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_purge_forced_impl(addr, offset, length);
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}
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#endif
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if (extent_hooks->purge_forced == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->purge_forced(extent_hooks, addr, size,
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offset, length, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline bool
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ehooks_split(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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size_t size_a, size_t size_b, bool committed, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (ehooks_are_default(ehooks)) {
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return ehooks_default_split_impl();
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} else if (extent_hooks->split == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->split(extent_hooks, addr, size, size_a,
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size_b, committed, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline bool
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ehooks_merge(tsdn_t *tsdn, ehooks_t *ehooks, void *addr_a, size_t size_a,
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void *addr_b, size_t size_b, bool committed, unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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return ehooks_default_merge_impl(addr_a, addr_b);
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} else if (extent_hooks->merge == NULL) {
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return true;
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} else {
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ehooks_pre_reentrancy(tsdn);
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bool err = extent_hooks->merge(extent_hooks, addr_a, size_a,
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addr_b, size_b, committed, arena_ind);
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ehooks_post_reentrancy(tsdn);
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return err;
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}
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}
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static inline void
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ehooks_zero(tsdn_t *tsdn, ehooks_t *ehooks, void *addr, size_t size,
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unsigned arena_ind) {
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extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
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if (extent_hooks == &ehooks_default_extent_hooks) {
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ehooks_default_zero_impl(addr, size);
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} else {
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/*
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* It would be correct to try using the user-provided purge
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* hooks (since they are required to have zeroed the extent if
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* they indicate success), but we don't necessarily know their
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* cost. We'll be conservative and use memset.
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*/
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memset(addr, 0, size);
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}
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}
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#endif /* JEMALLOC_INTERNAL_EHOOKS_H */
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