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https://gitlab.nic.cz/labs/bird.git
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794a4eefa1
On Linux, munmap() may fail with ENOMEM when virtual memory is too fragmented. Working this around by just keeping such blocks for future use.
138 lines
3.1 KiB
C
138 lines
3.1 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 <stdlib.h>
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#include <unistd.h>
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#include <stdatomic.h>
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#include <errno.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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_Bool alloc_multipage = 0;
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static _Atomic int global_page_list_not_empty;
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static list global_page_list;
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static _Atomic int global_page_spinlock;
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#define GLOBAL_PAGE_SPIN_LOCK for (int v = 0; !atomic_compare_exchange_weak_explicit(&global_page_spinlock, &v, 1, memory_order_acq_rel, memory_order_acquire); v = 0)
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#define GLOBAL_PAGE_SPIN_UNLOCK do { int v = 1; ASSERT_DIE(atomic_compare_exchange_strong_explicit(&global_page_spinlock, &v, 0, memory_order_acq_rel, memory_order_acquire)); } while (0)
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#ifdef HAVE_MMAP
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static _Bool use_fake = 0;
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#else
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static _Bool use_fake = 1;
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#endif
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void resource_sys_init(void)
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{
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#ifdef HAVE_MMAP
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init_list(&global_page_list);
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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 > 16384))
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#endif
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{
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/* Too big or strange page, use the aligned allocator instead */
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page_size = 4096;
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use_fake = 1;
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}
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}
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void *
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alloc_sys_page(void)
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{
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#ifdef HAVE_MMAP
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if (!use_fake)
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{
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if (atomic_load_explicit(&global_page_list_not_empty, memory_order_relaxed))
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{
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GLOBAL_PAGE_SPIN_LOCK;
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if (!EMPTY_LIST(global_page_list))
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{
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node *ret = HEAD(global_page_list);
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rem_node(ret);
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if (EMPTY_LIST(global_page_list))
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atomic_store_explicit(&global_page_list_not_empty, 0, memory_order_relaxed);
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GLOBAL_PAGE_SPIN_UNLOCK;
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memset(ret, 0, sizeof(node));
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return (void *) ret;
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}
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GLOBAL_PAGE_SPIN_UNLOCK;
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}
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if (alloc_multipage)
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{
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void *big = mmap(NULL, page_size * 2, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (big == MAP_FAILED)
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bug("mmap(%lu) failed: %m", page_size);
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uintptr_t offset = ((uintptr_t) big) % page_size;
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if (offset)
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{
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void *ret = big + page_size - offset;
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munmap(big, page_size - offset);
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munmap(ret + page_size, offset);
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return ret;
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}
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else
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{
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munmap(big + page_size, page_size);
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return big;
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}
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}
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void *ret = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
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if (ret == MAP_FAILED)
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bug("mmap(%lu) failed: %m", page_size);
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return ret;
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}
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else
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#endif
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{
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void *ret = aligned_alloc(page_size, page_size);
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if (!ret)
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bug("aligned_alloc(%lu) failed", page_size);
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return ret;
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}
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}
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void
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free_sys_page(void *ptr)
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{
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#ifdef HAVE_MMAP
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if (!use_fake)
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{
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if (munmap(ptr, page_size) < 0)
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#ifdef ENOMEM
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if (errno == ENOMEM)
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{
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memset(ptr, 0, page_size);
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GLOBAL_PAGE_SPIN_LOCK;
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add_tail(&global_page_list, (node *) ptr);
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atomic_store_explicit(&global_page_list_not_empty, 1, memory_order_relaxed);
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GLOBAL_PAGE_SPIN_UNLOCK;
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}
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else
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#endif
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bug("munmap(%p) failed: %m", ptr);
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}
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else
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#endif
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free(ptr);
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}
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