/*
* Copyright (C) the libgit2 contributors. All rights reserved.
*
* This file is part of libgit2, distributed under the GNU GPL v2 with
* a Linking Exception. For full terms see the included COPYING file.
*/
#include "mwindow.h"
#include "vector.h"
#include "futils.h"
#include "map.h"
#include "runtime.h"
#include "strmap.h"
#include "pack.h"
#define DEFAULT_WINDOW_SIZE \
(sizeof(void*) >= 8 \
? 1 * 1024 * 1024 * 1024 \
: 32 * 1024 * 1024)
#define DEFAULT_MAPPED_LIMIT \
((1024 * 1024) * (sizeof(void*) >= 8 ? UINT64_C(8192) : UINT64_C(256)))
/* default is unlimited */
#define DEFAULT_FILE_LIMIT 0
size_t git_mwindow__window_size = DEFAULT_WINDOW_SIZE;
size_t git_mwindow__mapped_limit = DEFAULT_MAPPED_LIMIT;
size_t git_mwindow__file_limit = DEFAULT_FILE_LIMIT;
/* Mutex to control access to `git_mwindow__mem_ctl` and `git__pack_cache`. */
git_mutex git__mwindow_mutex;
/* Whenever you want to read or modify this, grab `git__mwindow_mutex` */
git_mwindow_ctl git_mwindow__mem_ctl;
/* Global list of mwindow files, to open packs once across repos */
git_strmap *git__pack_cache = NULL;
static void git_mwindow_global_shutdown(void)
{
git_strmap *tmp = git__pack_cache;
git_mutex_free(&git__mwindow_mutex);
git__pack_cache = NULL;
git_strmap_free(tmp);
}
int git_mwindow_global_init(void)
{
int error;
GIT_ASSERT(!git__pack_cache);
if ((error = git_mutex_init(&git__mwindow_mutex)) < 0 ||
(error = git_strmap_new(&git__pack_cache)) < 0)
return error;
return git_runtime_shutdown_register(git_mwindow_global_shutdown);
}
int git_mwindow_get_pack(struct git_pack_file **out, const char *path)
{
struct git_pack_file *pack;
char *packname;
int error;
if ((error = git_packfile__name(&packname, path)) < 0)
return error;
if (git_mutex_lock(&git__mwindow_mutex) < 0) {
git_error_set(GIT_ERROR_OS, "failed to lock mwindow mutex");
return -1;
}
pack = git_strmap_get(git__pack_cache, packname);
git__free(packname);
if (pack != NULL) {
git_atomic32_inc(&pack->refcount);
git_mutex_unlock(&git__mwindow_mutex);
*out = pack;
return 0;
}
/* If we didn't find it, we need to create it */
if ((error = git_packfile_alloc(&pack, path)) < 0) {
git_mutex_unlock(&git__mwindow_mutex);
return error;
}
git_atomic32_inc(&pack->refcount);
error = git_strmap_set(git__pack_cache, pack->pack_name, pack);
git_mutex_unlock(&git__mwindow_mutex);
if (error < 0) {
git_packfile_free(pack, false);
return error;
}
*out = pack;
return 0;
}
int git_mwindow_put_pack(struct git_pack_file *pack)
{
int count, error;
struct git_pack_file *pack_to_delete = NULL;
if ((error = git_mutex_lock(&git__mwindow_mutex)) < 0)
return error;
/* put before get would be a corrupted state */
GIT_ASSERT(git__pack_cache);
/* if we cannot find it, the state is corrupted */
GIT_ASSERT(git_strmap_exists(git__pack_cache, pack->pack_name));
count = git_atomic32_dec(&pack->refcount);
if (count == 0) {
git_strmap_delete(git__pack_cache, pack->pack_name);
pack_to_delete = pack;
}
git_mutex_unlock(&git__mwindow_mutex);
git_packfile_free(pack_to_delete, false);
return 0;
}
/*
* Free all the windows in a sequence, typically because we're done
* with the file. Needs to hold the git__mwindow_mutex.
*/
static int git_mwindow_free_all_locked(git_mwindow_file *mwf)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
size_t i;
/*
* Remove these windows from the global list
*/
for (i = 0; i < ctl->windowfiles.length; ++i){
if (git_vector_get(&ctl->windowfiles, i) == mwf) {
git_vector_remove(&ctl->windowfiles, i);
break;
}
}
if (ctl->windowfiles.length == 0) {
git_vector_free(&ctl->windowfiles);
ctl->windowfiles.contents = NULL;
}
while (mwf->windows) {
git_mwindow *w = mwf->windows;
GIT_ASSERT(w->inuse_cnt == 0);
ctl->mapped -= w->window_map.len;
ctl->open_windows--;
git_futils_mmap_free(&w->window_map);
mwf->windows = w->next;
git__free(w);
}
return 0;
}
int git_mwindow_free_all(git_mwindow_file *mwf)
{
int error;
if (git_mutex_lock(&git__mwindow_mutex)) {
git_error_set(GIT_ERROR_THREAD, "unable to lock mwindow mutex");
return -1;
}
error = git_mwindow_free_all_locked(mwf);
git_mutex_unlock(&git__mwindow_mutex);
return error;
}
/*
* Check if a window 'win' contains the address 'offset'
*/
int git_mwindow_contains(git_mwindow *win, off64_t offset)
{
off64_t win_off = win->offset;
return win_off <= offset
&& offset <= (off64_t)(win_off + win->window_map.len);
}
#define GIT_MWINDOW__LRU -1
#define GIT_MWINDOW__MRU 1
/*
* Find the least- or most-recently-used window in a file that is not currently
* being used. The 'only_unused' flag controls whether the caller requires the
* file to only have unused windows. If '*out_window' is non-null, it is used as
* a starting point for the comparison.
*
* Returns whether such a window was found in the file.
*/
static bool git_mwindow_scan_recently_used(
git_mwindow_file *mwf,
git_mwindow **out_window,
git_mwindow **out_last,
bool only_unused,
int comparison_sign)
{
git_mwindow *w, *w_last;
git_mwindow *lru_window = NULL, *lru_last = NULL;
bool found = false;
GIT_ASSERT_ARG(mwf);
GIT_ASSERT_ARG(out_window);
lru_window = *out_window;
if (out_last)
lru_last = *out_last;
for (w_last = NULL, w = mwf->windows; w; w_last = w, w = w->next) {
if (w->inuse_cnt) {
if (only_unused)
return false;
/* This window is currently being used. Skip it. */
continue;
}
/*
* If the current one is more (or less) recent than the last one,
* store it in the output parameter. If lru_window is NULL,
* it's the first loop, so store it as well.
*/
if (!lru_window ||
(comparison_sign == GIT_MWINDOW__LRU && lru_window->last_used > w->last_used) ||
(comparison_sign == GIT_MWINDOW__MRU && lru_window->last_used < w->last_used)) {
lru_window = w;
lru_last = w_last;
found = true;
}
}
if (!found)
return false;
*out_window = lru_window;
if (out_last)
*out_last = lru_last;
return true;
}
/*
* Close the least recently used window (that is currently not being used) out
* of all the files. Called under lock from new_window_locked.
*/
static int git_mwindow_close_lru_window_locked(void)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
git_mwindow_file *cur;
size_t i;
git_mwindow *lru_window = NULL, *lru_last = NULL, **list = NULL;
git_vector_foreach(&ctl->windowfiles, i, cur) {
if (git_mwindow_scan_recently_used(
cur, &lru_window, &lru_last, false, GIT_MWINDOW__LRU)) {
list = &cur->windows;
}
}
if (!lru_window) {
git_error_set(GIT_ERROR_OS, "failed to close memory window; couldn't find LRU");
return -1;
}
ctl->mapped -= lru_window->window_map.len;
git_futils_mmap_free(&lru_window->window_map);
if (lru_last)
lru_last->next = lru_window->next;
else
*list = lru_window->next;
git__free(lru_window);
ctl->open_windows--;
return 0;
}
/*
* Finds the file that does not have any open windows AND whose
* most-recently-used window is the least-recently used one across all
* currently open files.
*
* Called under lock from new_window_locked.
*/
static int git_mwindow_find_lru_file_locked(git_mwindow_file **out)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
git_mwindow_file *lru_file = NULL, *current_file = NULL;
git_mwindow *lru_window = NULL;
size_t i;
git_vector_foreach(&ctl->windowfiles, i, current_file) {
git_mwindow *mru_window = NULL;
if (!git_mwindow_scan_recently_used(
current_file, &mru_window, NULL, true, GIT_MWINDOW__MRU)) {
continue;
}
if (!lru_window || lru_window->last_used > mru_window->last_used) {
lru_window = mru_window;
lru_file = current_file;
}
}
if (!lru_file) {
git_error_set(GIT_ERROR_OS, "failed to close memory window file; couldn't find LRU");
return -1;
}
*out = lru_file;
return 0;
}
/* This gets called under lock from git_mwindow_open */
static git_mwindow *new_window_locked(
git_file fd,
off64_t size,
off64_t offset)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
size_t walign = git_mwindow__window_size / 2;
off64_t len;
git_mwindow *w;
w = git__calloc(1, sizeof(*w));
if (w == NULL)
return NULL;
w->offset = (offset / walign) * walign;
len = size - w->offset;
if (len > (off64_t)git_mwindow__window_size)
len = (off64_t)git_mwindow__window_size;
ctl->mapped += (size_t)len;
while (git_mwindow__mapped_limit < ctl->mapped &&
git_mwindow_close_lru_window_locked() == 0) /* nop */;
/*
* We treat `mapped_limit` as a soft limit. If we can't find a
* window to close and are above the limit, we still mmap the new
* window.
*/
if (git_futils_mmap_ro(&w->window_map, fd, w->offset, (size_t)len) < 0) {
/*
* The first error might be down to memory fragmentation even if
* we're below our soft limits, so free up what we can and try again.
*/
while (git_mwindow_close_lru_window_locked() == 0)
/* nop */;
if (git_futils_mmap_ro(&w->window_map, fd, w->offset, (size_t)len) < 0) {
git__free(w);
return NULL;
}
}
ctl->mmap_calls++;
ctl->open_windows++;
if (ctl->mapped > ctl->peak_mapped)
ctl->peak_mapped = ctl->mapped;
if (ctl->open_windows > ctl->peak_open_windows)
ctl->peak_open_windows = ctl->open_windows;
return w;
}
/*
* Open a new window, closing the least recenty used until we have
* enough space. Don't forget to add it to your list
*/
unsigned char *git_mwindow_open(
git_mwindow_file *mwf,
git_mwindow **cursor,
off64_t offset,
size_t extra,
unsigned int *left)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
git_mwindow *w = *cursor;
if (git_mutex_lock(&git__mwindow_mutex)) {
git_error_set(GIT_ERROR_THREAD, "unable to lock mwindow mutex");
return NULL;
}
if (!w || !(git_mwindow_contains(w, offset) && git_mwindow_contains(w, offset + extra))) {
if (w) {
w->inuse_cnt--;
}
for (w = mwf->windows; w; w = w->next) {
if (git_mwindow_contains(w, offset) &&
git_mwindow_contains(w, offset + extra))
break;
}
/*
* If there isn't a suitable window, we need to create a new
* one.
*/
if (!w) {
w = new_window_locked(mwf->fd, mwf->size, offset);
if (w == NULL) {
git_mutex_unlock(&git__mwindow_mutex);
return NULL;
}
w->next = mwf->windows;
mwf->windows = w;
}
}
/* If we changed w, store it in the cursor */
if (w != *cursor) {
w->last_used = ctl->used_ctr++;
w->inuse_cnt++;
*cursor = w;
}
offset -= w->offset;
if (left)
*left = (unsigned int)(w->window_map.len - offset);
git_mutex_unlock(&git__mwindow_mutex);
return (unsigned char *) w->window_map.data + offset;
}
int git_mwindow_file_register(git_mwindow_file *mwf)
{
git_vector closed_files = GIT_VECTOR_INIT;
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
int error;
size_t i;
git_mwindow_file *closed_file = NULL;
if (git_mutex_lock(&git__mwindow_mutex)) {
git_error_set(GIT_ERROR_THREAD, "unable to lock mwindow mutex");
return -1;
}
if (ctl->windowfiles.length == 0 &&
(error = git_vector_init(&ctl->windowfiles, 8, NULL)) < 0) {
git_mutex_unlock(&git__mwindow_mutex);
goto cleanup;
}
if (git_mwindow__file_limit) {
git_mwindow_file *lru_file;
while (git_mwindow__file_limit <= ctl->windowfiles.length &&
git_mwindow_find_lru_file_locked(&lru_file) == 0) {
if ((error = git_vector_insert(&closed_files, lru_file)) < 0) {
/*
* Exceeding the file limit seems preferable to being open to
* data races that can end up corrupting the heap.
*/
break;
}
git_mwindow_free_all_locked(lru_file);
}
}
error = git_vector_insert(&ctl->windowfiles, mwf);
git_mutex_unlock(&git__mwindow_mutex);
if (error < 0)
goto cleanup;
/*
* Once we have released the global windowfiles lock, we can close each
* individual file. Before doing so, acquire that file's lock to avoid
* closing a file that is currently being used.
*/
git_vector_foreach(&closed_files, i, closed_file) {
error = git_mutex_lock(&closed_file->lock);
if (error < 0)
continue;
p_close(closed_file->fd);
closed_file->fd = -1;
git_mutex_unlock(&closed_file->lock);
}
cleanup:
git_vector_free(&closed_files);
return error;
}
void git_mwindow_file_deregister(git_mwindow_file *mwf)
{
git_mwindow_ctl *ctl = &git_mwindow__mem_ctl;
git_mwindow_file *cur;
size_t i;
if (git_mutex_lock(&git__mwindow_mutex))
return;
git_vector_foreach(&ctl->windowfiles, i, cur) {
if (cur == mwf) {
git_vector_remove(&ctl->windowfiles, i);
git_mutex_unlock(&git__mwindow_mutex);
return;
}
}
git_mutex_unlock(&git__mwindow_mutex);
}
void git_mwindow_close(git_mwindow **window)
{
git_mwindow *w = *window;
if (w) {
if (git_mutex_lock(&git__mwindow_mutex)) {
git_error_set(GIT_ERROR_THREAD, "unable to lock mwindow mutex");
return;
}
w->inuse_cnt--;
git_mutex_unlock(&git__mwindow_mutex);
*window = NULL;
}
}
