9eec503b25
When BIRD was munmapping too many pages, it sometimes aborted, saying that munmap failed with "Not enough memory" as the address space was getting more and more fragmented. There is a workaround in place, simply keeping that page for future use, yet it has never been compiled in because I somehow forgot to include errno.h. And because I also thought that somebody may have ENOMEM not defined (why?!), there was a check which quietly omitted that workaround. Anyway, ENOMEM is POSIX. It's an utter nonsense to check for its existence. If it doesn't exist, something is broken.
187 lines
3.6 KiB
C
187 lines
3.6 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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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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struct free_pages {
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list pages;
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u16 min, max; /* Minimal and maximal number of free pages kept */
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uint cnt; /* Number of empty pages */
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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 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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bug("mmap(%lu) failed: %m", 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 (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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bug("posix_memalign(%lu) failed", (long unsigned int) 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 (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 ((--fps->cnt < fps->min) && !shutting_down)
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ev_schedule(&fps->cleanup);
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bzero(fp, page_size);
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return fp;
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}
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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 (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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fp->n = (node) {};
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add_tail(&fps->pages, &fp->n);
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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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if (shutting_down)
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return;
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struct free_pages *fps = &global_free_pages;
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while (fps->cnt / 2 < fps->min)
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{
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struct free_page *fp = alloc_sys_page();
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fp->n = (node) {};
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add_tail(&fps->pages, &fp->n);
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fps->cnt++;
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}
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for (uint seen = 0; (seen < CLEANUP_PAGES_BULK) && (fps->cnt > fps->max / 2); seen++)
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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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if (munmap(fp, page_size) == 0)
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fps->cnt--;
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else if (errno == ENOMEM)
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add_head(&fps->pages, &fp->n);
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else
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bug("munmap(%p) failed: %m", fp);
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}
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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 HAVE_MMAP
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ASSERT_DIE(global_free_pages.cnt == 0);
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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)
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{
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struct free_pages *fps = &global_free_pages;
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init_list(&fps->pages);
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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 (%lu), using the aligned allocator instead", 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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