顺便说一句，文件/proc/1234/maps 向您显示pid 1234进程的内存映射.终端，它显示该 cat 进程的内存映射.I need to find a way to use mmap instead of malloc. How is this possible? (I am not using libc only syscalls) And yes brk() is possible. I used sbrk() but realized its not sys-call... (x86 inline assembly)I've been looking around and saw this: How to use mmap to allocate a memory in heap? But it didn't help for me, because I had a segfault.Basically, all I want to do a create 3 slabs of memory for storing characters.Say, char * x = malloc(1000);char * y = malloc(2000);char * z = malloc(3000);How is this possible with mmap and how to free it later with munmap? 解决方案 Did you carefully read the mmap(2) man page? I recommend reading it several times.Notice that you can only ask the kernel [thru mmap etc...] to manage memory aligned to and multiple of the page size sysconf(_SC_PAGE_SIZE) which is often 4096 bytes (and I am supposing that in my answer).Then you might do: size_t page_size = sysconf(_SC_PAGE_SIZE); assert (page_size == 4096); // otherwise this code is wrong // 1000 bytes fit into 1*4096 char *x = mmap (NULL, page_size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS, -1, (off_t)0); if (x == MMAP_FAILED) perror("mmap x"), exit (EXIT_FAILURE); // 2000 bytes fit into 1*4096 char *y = mmap (NULL, page_size, PROT_READ|PROT_WRITE, MAP_ANONYMOUS, -1, (off_t)0); if (y == MMAP_FAILED) perror("mmap y"), exit (EXIT_FAILURE);later to free the memory, use if (munmap(x, page_size)) perror("munmap x"), exit(EXIT_FAILURE);etcIf you want to allocate 5Kbytes, you'll need two pages (because 5Kbytes < 2*4096 and 5Kbytes > 1*4096) i.e. mmap(NULL, 2*page_size, ...Actually, all of your x, y, z takes only 8000 bytes and could fit into two, not three, pages... But then you could only munmap that memory together.Be aware that mmap is a system call which might be quite expensive. malloc implementations take care to avoid calling it too often, that is why they manage previously free-d zones to reuse them later (in further malloc-s) without any syscall. In practice, most malloc implementations manage differently big allocations (e.g. more than a megabyte), which are often mmap-ed at malloc and munmap-ed at free time.... You could study the source code of some malloc. The one from MUSL Libc might be easier to read than the Glibc malloc.BTW, the file /proc/1234/maps is showing you the memory map of process of pid 1234. Try also cat /proc/self/maps in a terminal, it shows the memory map of that cat process. 这篇关于mmap替代malloc的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！
