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* 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 "common.h"

#include "mwindow.h"

#include "vector.h"

#include "fileops.h"

#include "map.h"

#include "global.h"

#define DEFAULT_WINDOW_SIZE \

(sizeof(void*) >= 8 \

? 1 * 1024 * 1024 * 1024 \

: 32 * 1024 * 1024)

#define DEFAULT_MAPPED_LIMIT \

((1024 * 1024) * (sizeof(void*) >= 8 ? 8192ULL : 256UL))

size_t git_mwindow__window_size = DEFAULT_WINDOW_SIZE;

size_t git_mwindow__mapped_limit = DEFAULT_MAPPED_LIMIT;

/* Whenever you want to read or modify this, grab git__mwindow_mutex */

static git_mwindow_ctl mem_ctl;

* Free all the windows in a sequence, typically because we're done

* with the file

void git_mwindow_free_all(git_mwindow_file *mwf)

{

git_mwindow_ctl *ctl = &mem_ctl;

size_t i;

if (git_mutex_lock(&git__mwindow_mutex)) {

giterr_set(GITERR_THREAD, "unable to lock mwindow mutex");

return;

}

* 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;

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);

}

git_mutex_unlock(&git__mwindow_mutex);

}

* Check if a window 'win' contains the address 'offset'

int git_mwindow_contains(git_mwindow *win, git_off_t offset)

{

git_off_t win_off = win->offset;

return win_off <= offset

&& offset <= (git_off_t)(win_off + win->window_map.len);

}

* Find the least-recently-used window in a file

static void git_mwindow_scan_lru(

git_mwindow_file *mwf,

git_mwindow **lru_w,

git_mwindow **lru_l)

{

git_mwindow *w, *w_l;

for (w_l = NULL, w = mwf->windows; w; w = w->next) {

if (!w->inuse_cnt) {

* If the current one is more recent than the last one,

* store it in the output parameter. If lru_w is NULL,

* it's the first loop, so store it as well.

if (!*lru_w || w->last_used < (*lru_w)->last_used) {

*lru_w = w;

*lru_l = w_l;

}

w_l = w;

}

* Close the least recently used window. You should check to see if

* the file descriptors need closing from time to time. Called under

* lock from new_window.

static int git_mwindow_close_lru(git_mwindow_file *mwf)

{

git_mwindow_ctl *ctl = &mem_ctl;

size_t i;

git_mwindow *lru_w = NULL, *lru_l = NULL, **list = &mwf->windows;

/* FIXME: Does this give us any advantage? */

if(mwf->windows)

git_mwindow_scan_lru(mwf, &lru_w, &lru_l);

for (i = 0; i < ctl->windowfiles.length; ++i) {

git_mwindow *last = lru_w;

git_mwindow_file *cur = git_vector_get(&ctl->windowfiles, i);

git_mwindow_scan_lru(cur, &lru_w, &lru_l);

if (lru_w != last)

list = &cur->windows;

}

if (!lru_w) {

giterr_set(GITERR_OS, "Failed to close memory window. Couldn't find LRU");

return -1;

}

ctl->mapped -= lru_w->window_map.len;

git_futils_mmap_free(&lru_w->window_map);

if (lru_l)

lru_l->next = lru_w->next;

else

*list = lru_w->next;

git__free(lru_w);

ctl->open_windows--;

return 0;

}

/* This gets called under lock from git_mwindow_open */

static git_mwindow *new_window(

git_mwindow_file *mwf,

git_file fd,

git_off_t size,

git_off_t offset)

{

git_mwindow_ctl *ctl = &mem_ctl;

size_t walign = git_mwindow__window_size / 2;

git_off_t len;

git_mwindow *w;

w = git__malloc(sizeof(*w));

if (w == NULL)

return NULL;

memset(w, 0x0, sizeof(*w));

w->offset = (offset / walign) * walign;

len = size - w->offset;

if (len > (git_off_t)git_mwindow__window_size)

len = (git_off_t)git_mwindow__window_size;

ctl->mapped += (size_t)len;

while (git_mwindow__mapped_limit < ctl->mapped &&

git_mwindow_close_lru(mwf) == 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) {

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,

git_off_t offset,

size_t extra,

unsigned int *left)

{

git_mwindow_ctl *ctl = &mem_ctl;

git_mwindow *w = *cursor;

if (git_mutex_lock(&git__mwindow_mutex)) {

giterr_set(GITERR_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(mwf, 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_mwindow_ctl *ctl = &mem_ctl;

int ret;

if (git_mutex_lock(&git__mwindow_mutex)) {

giterr_set(GITERR_THREAD, "unable to lock mwindow mutex");

return -1;

}

if (ctl->windowfiles.length == 0 &&

git_vector_init(&ctl->windowfiles, 8, NULL) < 0) {

git_mutex_unlock(&git__mwindow_mutex);

return -1;

}

ret = git_vector_insert(&ctl->windowfiles, mwf);

git_mutex_unlock(&git__mwindow_mutex);

return ret;

}

void git_mwindow_file_deregister(git_mwindow_file *mwf)

{

git_mwindow_ctl *ctl = &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)) {

giterr_set(GITERR_THREAD, "unable to lock mwindow mutex");

return;

}

w->inuse_cnt--;

git_mutex_unlock(&git__mwindow_mutex);

*window = NULL;

}

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