mirror of
https://gitlab.nic.cz/labs/bird.git
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265 lines
6.7 KiB
C
265 lines
6.7 KiB
C
/*
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* BIRD Internet Routing Daemon -- Raw allocation
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*
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* (c) 2020 Maria Matejka <mq@ucw.cz>
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*
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* Can be freely distributed and used under the terms of the GNU GPL.
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*/
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#include "nest/bird.h"
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#include "lib/resource.h"
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#include "lib/lists.h"
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#include "lib/event.h"
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#include <errno.h>
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#include <stdlib.h>
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#include <unistd.h>
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#ifdef HAVE_MMAP
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#include <sys/mman.h>
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#endif
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#ifdef CONFIG_DISABLE_THP
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#include <sys/prctl.h>
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#ifndef PR_SET_THP_DISABLE
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#define PR_SET_THP_DISABLE 41
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#endif
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#endif
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long page_size = 0;
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#ifdef HAVE_MMAP
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#define KEEP_PAGES_MAIN_MAX 256
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#define KEEP_PAGES_MAIN_MIN 8
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#define CLEANUP_PAGES_BULK 256
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STATIC_ASSERT(KEEP_PAGES_MAIN_MIN * 4 < KEEP_PAGES_MAIN_MAX);
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static bool use_fake = 0;
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#if DEBUGGING
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struct free_page {
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node unused[42];
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node n;
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};
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#else
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struct free_page {
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node n;
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};
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#endif
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#define EP_POS_MAX ((page_size - OFFSETOF(struct empty_pages, pages)) / sizeof (void *))
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struct empty_pages {
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node n;
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uint pos;
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void *pages[0];
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};
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struct free_pages {
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list pages; /* List of (struct free_page) keeping free pages without releasing them (hot) */
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list empty; /* List of (struct empty_pages) keeping invalidated pages mapped for us (cold) */
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u16 min, max; /* Minimal and maximal number of free pages kept */
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uint cnt; /* Number of free pages in list */
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event cleanup;
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};
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static void global_free_pages_cleanup_event(void *);
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static void *alloc_cold_page(void);
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static struct free_pages global_free_pages = {
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.min = KEEP_PAGES_MAIN_MIN,
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.max = KEEP_PAGES_MAIN_MAX,
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.cleanup = { .hook = global_free_pages_cleanup_event },
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};
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uint *pages_kept = &global_free_pages.cnt;
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static void *
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alloc_sys_page(void)
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{
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void *ptr = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (ptr == MAP_FAILED)
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die("mmap(%ld) failed: %m", (s64) page_size);
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return ptr;
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}
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extern int shutting_down; /* Shutdown requested. */
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#else // ! HAVE_MMAP
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#define use_fake 1
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#endif
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void *
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alloc_page(void)
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{
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/* If the system page allocator is goofy, we use posix_memalign to get aligned blocks of memory. */
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if (use_fake)
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{
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void *ptr = NULL;
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int err = posix_memalign(&ptr, page_size, page_size);
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if (err || !ptr)
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die("posix_memalign(%ld) failed", (s64) page_size);
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return ptr;
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}
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#ifdef HAVE_MMAP
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struct free_pages *fps = &global_free_pages;
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/* If there is any free page kept hot, we use it. */
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if (fps->cnt)
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{
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struct free_page *fp = SKIP_BACK(struct free_page, n, HEAD(fps->pages));
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rem_node(&fp->n);
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/* If the hot-free-page cache is getting short, request the cleanup routine to replenish the cache */
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if ((--fps->cnt < fps->min) && !shutting_down)
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ev_schedule(&fps->cleanup);
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return fp;
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}
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else
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return alloc_cold_page();
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}
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static void *
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alloc_cold_page(void)
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{
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struct free_pages *fps = &global_free_pages;
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/* If there is any free page kept cold, we use that. */
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if (!EMPTY_LIST(fps->empty))
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{
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struct empty_pages *ep = HEAD(fps->empty);
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/* Either the keeper page contains at least one cold page pointer, return that */
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if (ep->pos)
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return ep->pages[--ep->pos];
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/* Or the keeper page has no more cold page pointer, return the keeper page */
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rem_node(&ep->n);
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return ep;
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}
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/* And in the worst case, allocate a new page by mmap() */
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return alloc_sys_page();
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#endif
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}
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void
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free_page(void *ptr)
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{
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/* If the system page allocator is goofy, we just free the block and care no more. */
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if (use_fake)
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{
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free(ptr);
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return;
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}
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#ifdef HAVE_MMAP
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struct free_pages *fps = &global_free_pages;
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struct free_page *fp = ptr;
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/* Otherwise, we add the free page to the hot-free-page list */
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fp->n = (node) {};
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add_tail(&fps->pages, &fp->n);
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/* And if there are too many hot free pages, we ask for page cleanup */
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if ((++fps->cnt > fps->max) && !shutting_down)
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ev_schedule(&fps->cleanup);
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#endif
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}
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#ifdef HAVE_MMAP
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static void
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global_free_pages_cleanup_event(void *data UNUSED)
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{
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/* Cleanup on shutdown is ignored. All pages may be kept hot, OS will take care. */
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if (shutting_down)
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return;
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struct free_pages *fps = &global_free_pages;
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/* Cleanup may get called when hot free page cache is short of pages. Replenishing. */
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while (fps->cnt / 2 < fps->min)
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free_page(alloc_cold_page());
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/* Or the hot free page cache is too big. Moving some pages to the cold free page cache. */
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for (int limit = CLEANUP_PAGES_BULK; limit && (fps->cnt > fps->max / 2); fps->cnt--, limit--)
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{
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struct free_page *fp = SKIP_BACK(struct free_page, n, TAIL(fps->pages));
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rem_node(&fp->n);
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/* Empty pages are stored as pointers. To store them, we need a pointer block. */
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struct empty_pages *ep;
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if (EMPTY_LIST(fps->empty) || ((ep = HEAD(fps->empty))->pos == EP_POS_MAX))
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{
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/* There is either no pointer block or the last block is full. We use this block as a pointer block. */
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ep = (struct empty_pages *) fp;
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*ep = (struct empty_pages) {};
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add_head(&fps->empty, &ep->n);
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}
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else
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{
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/* We store this block as a pointer into the first free place
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* and tell the OS that the underlying memory is trash. */
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ep->pages[ep->pos++] = fp;
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if (madvise(fp, page_size,
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#ifdef CONFIG_MADV_DONTNEED_TO_FREE
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MADV_DONTNEED
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#else
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MADV_FREE
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#endif
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) < 0)
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bug("madvise(%p) failed: %m", fp);
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}
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}
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/* If the hot free page cleanup hit the limit, re-schedule this routine
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* to allow for other routines to run. */
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if (fps->cnt > fps->max)
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ev_schedule(&fps->cleanup);
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}
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#endif
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void
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resource_sys_init(void)
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{
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#ifdef CONFIG_DISABLE_THP
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/* Disable transparent huge pages, they do not work properly with madvice(MADV_DONTNEED) */
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if (prctl(PR_SET_THP_DISABLE, (unsigned long) 1, (unsigned long) 0, (unsigned long) 0, (unsigned long) 0) < 0)
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log(L_WARN "Cannot disable transparent huge pages: prctl(PR_SET_THP_DISABLE) failed: %m");
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#endif
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#ifdef HAVE_MMAP
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ASSERT_DIE(global_free_pages.cnt == 0);
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/* Check what page size the system supports */
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if (!(page_size = sysconf(_SC_PAGESIZE)))
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die("System page size must be non-zero");
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if ((u64_popcount(page_size) == 1) && (page_size >= (1 << 10)) && (page_size <= (1 << 18)))
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{
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/* We assume that page size has only one bit and is between 1K and 256K (incl.).
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* Otherwise, the assumptions in lib/slab.c (sl_head's num_full range) aren't met. */
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struct free_pages *fps = &global_free_pages;
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init_list(&fps->pages);
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init_list(&fps->empty);
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global_free_pages_cleanup_event(NULL);
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return;
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}
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/* Too big or strange page, use the aligned allocator instead */
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log(L_WARN "Got strange memory page size (%ld), using the aligned allocator instead", (s64) page_size);
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use_fake = 1;
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#endif
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page_size = 4096;
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}
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