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Make fork() go 30% faster

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This change makes fork() go nearly as fast as sys_fork() on UNIX. As for
Windows this change shaves about 4-5ms off fork() + wait() latency. This
is accomplished by using WriteProcessMemory() from the parent process to
setup the address space of a suspended process; it is better than a pipe
This commit is contained in:
Justine Tunney 2025-01-01 04:59:38 -08:00
parent 98c5847727
commit 0b3c81dd4e
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GPG key ID: BE714B4575D6E328
44 changed files with 769 additions and 649 deletions
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43
libc/intrin/maps.h
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@ -5,6 +5,28 @@
#include "libc/runtime/runtime.h"
COSMOPOLITAN_C_START_
/* size of dynamic memory that is used internally by your memory manager */
#define MAPS_SIZE 65536
/* when map->hand is MAPS_RESERVATION it means mmap() is transactionally
reserving address space it is in the process of requesting from win32 */
#define MAPS_RESERVATION -2
/* when map->hand is MAPS_SUBREGION it means that an allocation has been
broken into multiple fragments by mprotect(). the first fragment must
be set to MAPS_VIRTUAL or your CreateFileMapping() handle. your frags
must be perfectly contiguous in memory and should have the same flags */
#define MAPS_SUBREGION -3
/* indicates an allocation was created by VirtualAlloc() and so munmap()
must call VirtualFree() when destroying it. use it on the hand field. */
#define MAPS_VIRTUAL -4
/* if this is used on MAP_PRIVATE memory, then it's assumed to be memory
that win32 allocated, e.g. a CreateThread() stack. if this is used on
MAP_FILE memory, then it's assumed to be part of the executable image */
#define MAP_NOFORK 0x10000000
#define MAP_TREE_CONTAINER(e) TREE_CONTAINER(struct Map, tree, e)
struct Map {
@ -12,9 +34,8 @@ struct Map {
size_t size; /* must be nonzero */
int64_t off; /* ignore for anon */
int flags; /* memory map flag */
char prot; /* memory protects */
short prot; /* memory protects */
bool iscow; /* windows nt only */
bool precious; /* windows nt only */
bool readonlyfile; /* windows nt only */
unsigned visited; /* checks and fork */
intptr_t hand; /* windows nt only */
@ -29,11 +50,17 @@ struct MapLock {
_Atomic(uint64_t) word;
};
struct MapSlab {
struct MapSlab *next;
struct Map maps[(MAPS_SIZE - sizeof(struct MapSlab *)) / sizeof(struct Map)];
};
struct Maps {
uint128_t rand;
struct Tree *maps;
struct MapLock lock;
_Atomic(uintptr_t) freed;
_Atomic(struct MapSlab *) slabs;
size_t count;
size_t pages;
struct Map stack;
@ -76,33 +103,37 @@ forceinline optimizespeed int __maps_search(const void *key,
return (addr > map->addr) - (addr < map->addr);
}
static inline struct Map *__maps_next(struct Map *map) {
dontinstrument static inline struct Map *__maps_next(struct Map *map) {
struct Tree *node;
if ((node = tree_next(&map->tree)))
return MAP_TREE_CONTAINER(node);
return 0;
}
static inline struct Map *__maps_prev(struct Map *map) {
dontinstrument static inline struct Map *__maps_prev(struct Map *map) {
struct Tree *node;
if ((node = tree_prev(&map->tree)))
return MAP_TREE_CONTAINER(node);
return 0;
}
static inline struct Map *__maps_first(void) {
dontinstrument static inline struct Map *__maps_first(void) {
struct Tree *node;
if ((node = tree_first(__maps.maps)))
return MAP_TREE_CONTAINER(node);
return 0;
}
static inline struct Map *__maps_last(void) {
dontinstrument static inline struct Map *__maps_last(void) {
struct Tree *node;
if ((node = tree_last(__maps.maps)))
return MAP_TREE_CONTAINER(node);
return 0;
}
static inline bool __maps_isalloc(struct Map *map) {
return map->hand != MAPS_SUBREGION;
}
COSMOPOLITAN_C_END_
#endif /* COSMOPOLITAN_MAPS_H_ */