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/*
* BIRD Internet Routing Daemon -- Raw allocation
*
* (c) 2020 Maria Matejka <mq@ucw.cz>
*
* Can be freely distributed and used under the terms of the GNU GPL.
*/
#include "nest/bird.h"
#include "lib/resource.h"
#include "lib/lists.h"
#include "lib/event.h"
#include <errno.h>
#include <stdlib.h>
#include <unistd.h>
#ifdef HAVE_MMAP
#include <sys/mman.h>
#endif
long page_size = 0;
#ifdef HAVE_MMAP
#define KEEP_PAGES_MAIN_MAX 256
#define KEEP_PAGES_MAIN_MIN 8
#define CLEANUP_PAGES_BULK 256
STATIC_ASSERT(KEEP_PAGES_MAIN_MIN * 4 < KEEP_PAGES_MAIN_MAX);
static _Bool use_fake = 0;
#if DEBUGGING
struct free_page {
node unused[42];
node n;
};
#else
struct free_page {
node n;
};
#endif
#define EP_POS_MAX ((page_size - OFFSETOF(struct empty_pages, pages)) / sizeof (void *))
struct empty_pages {
node n;
uint pos;
void *pages[0];
};
struct free_pages {
list pages;
list empty;
u16 min, max; /* Minimal and maximal number of free pages kept */
uint cnt; /* Number of empty pages */
event cleanup;
};
static void global_free_pages_cleanup_event(void *);
static struct free_pages global_free_pages = {
.min = KEEP_PAGES_MAIN_MIN,
.max = KEEP_PAGES_MAIN_MAX,
.cleanup = { .hook = global_free_pages_cleanup_event },
};
uint *pages_kept = &global_free_pages.cnt;
static void *
alloc_sys_page(void)
{
void *ptr = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
if (ptr == MAP_FAILED)
bug("mmap(%lu) failed: %m", page_size);
return ptr;
}
extern int shutting_down; /* Shutdown requested. */
#else // ! HAVE_MMAP
#define use_fake 1
#endif
void *
alloc_page(void)
{
if (use_fake)
{
void *ptr = NULL;
int err = posix_memalign(&ptr, page_size, page_size);
if (err || !ptr)
bug("posix_memalign(%lu) failed", (long unsigned int) page_size);
return ptr;
}
#ifdef HAVE_MMAP
struct free_pages *fps = &global_free_pages;
if (fps->cnt)
{
struct free_page *fp = SKIP_BACK(struct free_page, n, HEAD(fps->pages));
rem_node(&fp->n);
if ((--fps->cnt < fps->min) && !shutting_down)
ev_schedule(&fps->cleanup);
bzero(fp, page_size);
return fp;
}
if (!EMPTY_LIST(fps->empty))
{
struct empty_pages *ep = HEAD(fps->empty);
if (ep->pos)
return ep->pages[--ep->pos];
rem_node(&ep->n);
return ep;
}
return alloc_sys_page();
#endif
}
void
free_page(void *ptr)
{
if (use_fake)
{
free(ptr);
return;
}
#ifdef HAVE_MMAP
struct free_pages *fps = &global_free_pages;
struct free_page *fp = ptr;
fp->n = (node) {};
add_tail(&fps->pages, &fp->n);
if ((++fps->cnt > fps->max) && !shutting_down)
ev_schedule(&fps->cleanup);
#endif
}
#ifdef HAVE_MMAP
static void
global_free_pages_cleanup_event(void *data UNUSED)
{
if (shutting_down)
return;
struct free_pages *fps = &global_free_pages;
while (fps->cnt / 2 < fps->min)
{
struct free_page *fp = alloc_sys_page();
fp->n = (node) {};
add_tail(&fps->pages, &fp->n);
fps->cnt++;
}
int limit = CLEANUP_PAGES_BULK;
while (--limit && (fps->cnt > fps->max / 2))
{
struct free_page *fp = SKIP_BACK(struct free_page, n, TAIL(fps->pages));
rem_node(&fp->n);
fps->cnt--;
struct empty_pages *ep;
if (EMPTY_LIST(fps->empty) || ((ep = HEAD(fps->empty))->pos == EP_POS_MAX))
{
ep = (struct empty_pages *) fp;
*ep = (struct empty_pages) {};
add_head(&fps->empty, &ep->n);
}
else
{
ep->pages[ep->pos++] = fp;
if (madvise(fp, page_size,
#ifdef CONFIG_MADV_DONTNEED_TO_FREE
MADV_DONTNEED
#else
MADV_FREE
#endif
) < 0)
bug("madvise(%p) failed: %m", fp);
}
}
if (!limit)
ev_schedule(&fps->cleanup);
}
#endif
void
resource_sys_init(void)
{
#ifdef HAVE_MMAP
ASSERT_DIE(global_free_pages.cnt == 0);
if (!(page_size = sysconf(_SC_PAGESIZE)))
die("System page size must be non-zero");
if (u64_popcount(page_size) == 1)
{
struct free_pages *fps = &global_free_pages;
init_list(&fps->pages);
init_list(&fps->empty);
global_free_pages_cleanup_event(NULL);
return;
}
/* Too big or strange page, use the aligned allocator instead */
log(L_WARN "Got strange memory page size (%lu), using the aligned allocator instead", page_size);
use_fake = 1;
#endif
page_size = 4096;
}
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