server-skynet-source-3rd-je.../include/jemalloc/internal/ph.h
Kevin Svetlitski 41e0b857be Make headers self-contained by fixing #includes
Header files are now self-contained, which makes the relationships
between the files clearer, and crucially allows LSP tools like `clangd`
to function correctly in all of our header files. I have verified that
the headers are self-contained (aside from the various Windows shims) by
compiling them as if they were C files – in a follow-up commit I plan to
add this to CI to ensure we don't regress on this front.
2023-07-14 09:06:32 -07:00

505 lines
14 KiB
C

#ifndef JEMALLOC_INTERNAL_PH_H
#define JEMALLOC_INTERNAL_PH_H
#include "jemalloc/internal/jemalloc_preamble.h"
#include "jemalloc/internal/assert.h"
#include "jemalloc/internal/bit_util.h"
/*
* A Pairing Heap implementation.
*
* "The Pairing Heap: A New Form of Self-Adjusting Heap"
* https://www.cs.cmu.edu/~sleator/papers/pairing-heaps.pdf
*
* With auxiliary twopass list, described in a follow on paper.
*
* "Pairing Heaps: Experiments and Analysis"
* http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.106.2988&rep=rep1&type=pdf
*
*******************************************************************************
*
* We include a non-obvious optimization:
* - First, we introduce a new pop-and-link operation; pop the two most
* recently-inserted items off the aux-list, link them, and push the resulting
* heap.
* - We maintain a count of the number of insertions since the last time we
* merged the aux-list (i.e. via first() or remove_first()). After N inserts,
* we do ffs(N) pop-and-link operations.
*
* One way to think of this is that we're progressively building up a tree in
* the aux-list, rather than a linked-list (think of the series of merges that
* will be performed as the aux-count grows).
*
* There's a couple reasons we benefit from this:
* - Ordinarily, after N insertions, the aux-list is of size N. With our
* strategy, it's of size O(log(N)). So we decrease the worst-case time of
* first() calls, and reduce the average cost of remove_min calls. Since
* these almost always occur while holding a lock, we practically reduce the
* frequency of unusually long hold times.
* - This moves the bulk of the work of merging the aux-list onto the threads
* that are inserting into the heap. In some common scenarios, insertions
* happen in bulk, from a single thread (think tcache flushing; we potentially
* move many slabs from slabs_full to slabs_nonfull). All the nodes in this
* case are in the inserting threads cache, and linking them is very cheap
* (cache misses dominate linking cost). Without this optimization, linking
* happens on the next call to remove_first. Since that remove_first call
* likely happens on a different thread (or at least, after the cache has
* gotten cold if done on the same thread), deferring linking trades cheap
* link operations now for expensive ones later.
*
* The ffs trick keeps amortized insert cost at constant time. Similar
* strategies based on periodically sorting the list after a batch of operations
* perform worse than this in practice, even with various fancy tricks; they
* all took amortized complexity of an insert from O(1) to O(log(n)).
*/
typedef int (*ph_cmp_t)(void *, void *);
/* Node structure. */
typedef struct phn_link_s phn_link_t;
struct phn_link_s {
void *prev;
void *next;
void *lchild;
};
typedef struct ph_s ph_t;
struct ph_s {
void *root;
/*
* Inserts done since the last aux-list merge. This is not necessarily
* the size of the aux-list, since it's possible that removals have
* happened since, and we don't track whether or not those removals are
* from the aux list.
*/
size_t auxcount;
};
JEMALLOC_ALWAYS_INLINE phn_link_t *
phn_link_get(void *phn, size_t offset) {
return (phn_link_t *)(((char *)phn) + offset);
}
JEMALLOC_ALWAYS_INLINE void
phn_link_init(void *phn, size_t offset) {
phn_link_get(phn, offset)->prev = NULL;
phn_link_get(phn, offset)->next = NULL;
phn_link_get(phn, offset)->lchild = NULL;
}
/* Internal utility helpers. */
JEMALLOC_ALWAYS_INLINE void *
phn_lchild_get(void *phn, size_t offset) {
return phn_link_get(phn, offset)->lchild;
}
JEMALLOC_ALWAYS_INLINE void
phn_lchild_set(void *phn, void *lchild, size_t offset) {
phn_link_get(phn, offset)->lchild = lchild;
}
JEMALLOC_ALWAYS_INLINE void *
phn_next_get(void *phn, size_t offset) {
return phn_link_get(phn, offset)->next;
}
JEMALLOC_ALWAYS_INLINE void
phn_next_set(void *phn, void *next, size_t offset) {
phn_link_get(phn, offset)->next = next;
}
JEMALLOC_ALWAYS_INLINE void *
phn_prev_get(void *phn, size_t offset) {
return phn_link_get(phn, offset)->prev;
}
JEMALLOC_ALWAYS_INLINE void
phn_prev_set(void *phn, void *prev, size_t offset) {
phn_link_get(phn, offset)->prev = prev;
}
JEMALLOC_ALWAYS_INLINE void
phn_merge_ordered(void *phn0, void *phn1, size_t offset,
ph_cmp_t cmp) {
void *phn0child;
assert(phn0 != NULL);
assert(phn1 != NULL);
assert(cmp(phn0, phn1) <= 0);
phn_prev_set(phn1, phn0, offset);
phn0child = phn_lchild_get(phn0, offset);
phn_next_set(phn1, phn0child, offset);
if (phn0child != NULL) {
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_prev_set(phn0child, phn1, offset);
}
phn_lchild_set(phn0, phn1, offset);
}
JEMALLOC_ALWAYS_INLINE void *
phn_merge(void *phn0, void *phn1, size_t offset, ph_cmp_t cmp) {
void *result;
if (phn0 == NULL) {
result = phn1;
} else if (phn1 == NULL) {
result = phn0;
} else if (cmp(phn0, phn1) < 0) {
phn_merge_ordered(phn0, phn1, offset, cmp);
result = phn0;
} else {
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_merge_ordered(phn1, phn0, offset, cmp);
result = phn1;
}
return result;
}
JEMALLOC_ALWAYS_INLINE void *
phn_merge_siblings(void *phn, size_t offset, ph_cmp_t cmp) {
void *head = NULL;
void *tail = NULL;
void *phn0 = phn;
void *phn1 = phn_next_get(phn0, offset);
/*
* Multipass merge, wherein the first two elements of a FIFO
* are repeatedly merged, and each result is appended to the
* singly linked FIFO, until the FIFO contains only a single
* element. We start with a sibling list but no reference to
* its tail, so we do a single pass over the sibling list to
* populate the FIFO.
*/
if (phn1 != NULL) {
void *phnrest = phn_next_get(phn1, offset);
if (phnrest != NULL) {
phn_prev_set(phnrest, NULL, offset);
}
phn_prev_set(phn0, NULL, offset);
phn_next_set(phn0, NULL, offset);
phn_prev_set(phn1, NULL, offset);
phn_next_set(phn1, NULL, offset);
phn0 = phn_merge(phn0, phn1, offset, cmp);
head = tail = phn0;
phn0 = phnrest;
while (phn0 != NULL) {
phn1 = phn_next_get(phn0, offset);
if (phn1 != NULL) {
phnrest = phn_next_get(phn1, offset);
if (phnrest != NULL) {
phn_prev_set(phnrest, NULL, offset);
}
phn_prev_set(phn0, NULL, offset);
phn_next_set(phn0, NULL, offset);
phn_prev_set(phn1, NULL, offset);
phn_next_set(phn1, NULL, offset);
phn0 = phn_merge(phn0, phn1, offset, cmp);
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_next_set(tail, phn0, offset);
tail = phn0;
phn0 = phnrest;
} else {
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_next_set(tail, phn0, offset);
tail = phn0;
phn0 = NULL;
}
}
phn0 = head;
phn1 = phn_next_get(phn0, offset);
if (phn1 != NULL) {
while (true) {
head = phn_next_get(phn1, offset);
assert(phn_prev_get(phn0, offset) == NULL);
phn_next_set(phn0, NULL, offset);
assert(phn_prev_get(phn1, offset) == NULL);
phn_next_set(phn1, NULL, offset);
phn0 = phn_merge(phn0, phn1, offset, cmp);
if (head == NULL) {
break;
}
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_next_set(tail, phn0, offset);
tail = phn0;
phn0 = head;
phn1 = phn_next_get(phn0, offset);
}
}
}
return phn0;
}
JEMALLOC_ALWAYS_INLINE void
ph_merge_aux(ph_t *ph, size_t offset, ph_cmp_t cmp) {
ph->auxcount = 0;
void *phn = phn_next_get(ph->root, offset);
if (phn != NULL) {
phn_prev_set(ph->root, NULL, offset);
phn_next_set(ph->root, NULL, offset);
phn_prev_set(phn, NULL, offset);
phn = phn_merge_siblings(phn, offset, cmp);
assert(phn_next_get(phn, offset) == NULL);
ph->root = phn_merge(ph->root, phn, offset, cmp);
}
}
JEMALLOC_ALWAYS_INLINE void *
ph_merge_children(void *phn, size_t offset, ph_cmp_t cmp) {
void *result;
void *lchild = phn_lchild_get(phn, offset);
if (lchild == NULL) {
result = NULL;
} else {
result = phn_merge_siblings(lchild, offset, cmp);
}
return result;
}
JEMALLOC_ALWAYS_INLINE void
ph_new(ph_t *ph) {
ph->root = NULL;
ph->auxcount = 0;
}
JEMALLOC_ALWAYS_INLINE bool
ph_empty(ph_t *ph) {
return ph->root == NULL;
}
JEMALLOC_ALWAYS_INLINE void *
ph_first(ph_t *ph, size_t offset, ph_cmp_t cmp) {
if (ph->root == NULL) {
return NULL;
}
ph_merge_aux(ph, offset, cmp);
return ph->root;
}
JEMALLOC_ALWAYS_INLINE void *
ph_any(ph_t *ph, size_t offset) {
if (ph->root == NULL) {
return NULL;
}
void *aux = phn_next_get(ph->root, offset);
if (aux != NULL) {
return aux;
}
return ph->root;
}
/* Returns true if we should stop trying to merge. */
JEMALLOC_ALWAYS_INLINE bool
ph_try_aux_merge_pair(ph_t *ph, size_t offset, ph_cmp_t cmp) {
assert(ph->root != NULL);
void *phn0 = phn_next_get(ph->root, offset);
if (phn0 == NULL) {
return true;
}
void *phn1 = phn_next_get(phn0, offset);
if (phn1 == NULL) {
return true;
}
void *next_phn1 = phn_next_get(phn1, offset);
phn_next_set(phn0, NULL, offset);
phn_prev_set(phn0, NULL, offset);
phn_next_set(phn1, NULL, offset);
phn_prev_set(phn1, NULL, offset);
phn0 = phn_merge(phn0, phn1, offset, cmp);
phn_next_set(phn0, next_phn1, offset);
if (next_phn1 != NULL) {
/* NOLINTNEXTLINE(readability-suspicious-call-argument) */
phn_prev_set(next_phn1, phn0, offset);
}
phn_next_set(ph->root, phn0, offset);
phn_prev_set(phn0, ph->root, offset);
return next_phn1 == NULL;
}
JEMALLOC_ALWAYS_INLINE void
ph_insert(ph_t *ph, void *phn, size_t offset, ph_cmp_t cmp) {
phn_link_init(phn, offset);
/*
* Treat the root as an aux list during insertion, and lazily merge
* during a_prefix##remove_first(). For elements that are inserted,
* then removed via a_prefix##remove() before the aux list is ever
* processed, this makes insert/remove constant-time, whereas eager
* merging would make insert O(log n).
*/
if (ph->root == NULL) {
ph->root = phn;
return;
}
/*
* As a special case, check to see if we can replace the root.
* This is practically common in some important cases, and lets
* us defer some insertions (hopefully, until the point where
* some of the items in the aux list have been removed, savings
* us from linking them at all).
*/
if (cmp(phn, ph->root) < 0) {
phn_lchild_set(phn, ph->root, offset);
phn_prev_set(ph->root, phn, offset);
ph->root = phn;
ph->auxcount = 0;
return;
}
phn_next_set(phn, phn_next_get(ph->root, offset), offset);
if (phn_next_get(ph->root, offset) != NULL) {
phn_prev_set(phn_next_get(ph->root, offset), phn,
offset);
}
phn_prev_set(phn, ph->root, offset);
phn_next_set(ph->root, phn, offset);
ph->auxcount++;
unsigned nmerges = ffs_zu(ph->auxcount);
bool done = false;
for (unsigned i = 0; i < nmerges && !done; i++) {
done = ph_try_aux_merge_pair(ph, offset, cmp);
}
}
JEMALLOC_ALWAYS_INLINE void *
ph_remove_first(ph_t *ph, size_t offset, ph_cmp_t cmp) {
void *ret;
if (ph->root == NULL) {
return NULL;
}
ph_merge_aux(ph, offset, cmp);
ret = ph->root;
ph->root = ph_merge_children(ph->root, offset, cmp);
return ret;
}
JEMALLOC_ALWAYS_INLINE void
ph_remove(ph_t *ph, void *phn, size_t offset, ph_cmp_t cmp) {
if (ph->root == phn) {
/*
* We can delete from aux list without merging it, but we need
* to merge if we are dealing with the root node and it has
* children.
*/
if (phn_lchild_get(phn, offset) == NULL) {
ph->root = phn_next_get(phn, offset);
return;
}
ph_merge_aux(ph, offset, cmp);
if (ph->root == phn) {
ph->root = ph_merge_children(ph->root, offset, cmp);
return;
}
}
void* prev = phn_prev_get(phn, offset);
void* next = phn_next_get(phn, offset);
/* If we have children, then we integrate them back in the heap. */
void* replace = ph_merge_children(phn, offset, cmp);
if (replace != NULL) {
phn_next_set(replace, next, offset);
if (next != NULL) {
phn_prev_set(next, replace, offset);
}
next = replace;
}
if (next != NULL) {
phn_prev_set(next, prev, offset);
}
assert(prev != NULL);
if (phn_lchild_get(prev, offset) == phn) {
phn_lchild_set(prev, next, offset);
} else {
phn_next_set(prev, next, offset);
}
}
#define ph_structs(a_prefix, a_type) \
typedef struct { \
phn_link_t link; \
} a_prefix##_link_t; \
\
typedef struct { \
ph_t ph; \
} a_prefix##_t;
/*
* The ph_proto() macro generates function prototypes that correspond to the
* functions generated by an equivalently parameterized call to ph_gen().
*/
#define ph_proto(a_attr, a_prefix, a_type) \
\
a_attr void a_prefix##_new(a_prefix##_t *ph); \
a_attr bool a_prefix##_empty(a_prefix##_t *ph); \
a_attr a_type *a_prefix##_first(a_prefix##_t *ph); \
a_attr a_type *a_prefix##_any(a_prefix##_t *ph); \
a_attr void a_prefix##_insert(a_prefix##_t *ph, a_type *phn); \
a_attr a_type *a_prefix##_remove_first(a_prefix##_t *ph); \
a_attr void a_prefix##_remove(a_prefix##_t *ph, a_type *phn); \
a_attr a_type *a_prefix##_remove_any(a_prefix##_t *ph);
/* The ph_gen() macro generates a type-specific pairing heap implementation. */
#define ph_gen(a_attr, a_prefix, a_type, a_field, a_cmp) \
JEMALLOC_ALWAYS_INLINE int \
a_prefix##_ph_cmp(void *a, void *b) { \
return a_cmp((a_type *)a, (a_type *)b); \
} \
\
a_attr void \
a_prefix##_new(a_prefix##_t *ph) { \
ph_new(&ph->ph); \
} \
\
a_attr bool \
a_prefix##_empty(a_prefix##_t *ph) { \
return ph_empty(&ph->ph); \
} \
\
a_attr a_type * \
a_prefix##_first(a_prefix##_t *ph) { \
return ph_first(&ph->ph, offsetof(a_type, a_field), \
&a_prefix##_ph_cmp); \
} \
\
a_attr a_type * \
a_prefix##_any(a_prefix##_t *ph) { \
return ph_any(&ph->ph, offsetof(a_type, a_field)); \
} \
\
a_attr void \
a_prefix##_insert(a_prefix##_t *ph, a_type *phn) { \
ph_insert(&ph->ph, phn, offsetof(a_type, a_field), \
a_prefix##_ph_cmp); \
} \
\
a_attr a_type * \
a_prefix##_remove_first(a_prefix##_t *ph) { \
return ph_remove_first(&ph->ph, offsetof(a_type, a_field), \
a_prefix##_ph_cmp); \
} \
\
a_attr void \
a_prefix##_remove(a_prefix##_t *ph, a_type *phn) { \
ph_remove(&ph->ph, phn, offsetof(a_type, a_field), \
a_prefix##_ph_cmp); \
} \
\
a_attr a_type * \
a_prefix##_remove_any(a_prefix##_t *ph) { \
a_type *ret = a_prefix##_any(ph); \
if (ret != NULL) { \
a_prefix##_remove(ph, ret); \
} \
return ret; \
}
#endif /* JEMALLOC_INTERNAL_PH_H */