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Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually |
Date: |
Mon, 28 Oct 2013 14:48:13 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130923 Thunderbird/17.0.9 |
Il 08/10/2013 02:41, Marcelo Tosatti ha scritto:
> MAP_POPULATE mmap flag does not cause mmap to fail if allocation
> of the entire area is not performed. HugeTLBfs performs reservation
> of pages on a global basis: any further restriction to the reserved memory
> such as cpusets placement or numa node policy is performed at
> fault time only.
>
> Manually fault in pages at allocation time. This allows memory restrictions
> to be applied before guest initialization.
>
> Signed-off-by: Marcelo Tosatti <address@hidden>
>
> Index: qemu/exec.c
> ===================================================================
> --- qemu.orig/exec.c
> +++ qemu/exec.c
Please produce individual patches with git format-patch. This lets "git
am" do a 3-way merge, and would ignore automatically generated files
such as qemu-options.def.
Also:
> @@ -918,6 +918,13 @@ static long gethugepagesize(const char *
> return fs.f_bsize;
> }
>
> +sigjmp_buf sigjump;
Please make this static.
> +
> +static void sigbus_handler(int signal)
> +{
> + siglongjmp(sigjump, 1);
> +}
> +
> static void *file_ram_alloc(RAMBlock *block,
> ram_addr_t memory,
> const char *path)
> @@ -927,9 +934,6 @@ static void *file_ram_alloc(RAMBlock *bl
> char *c;
> void *area;
> int fd;
> -#ifdef MAP_POPULATE
> - int flags;
> -#endif
> unsigned long hpagesize;
>
> hpagesize = gethugepagesize(path);
> @@ -977,21 +981,57 @@ static void *file_ram_alloc(RAMBlock *bl
> if (ftruncate(fd, memory))
> perror("ftruncate");
>
> -#ifdef MAP_POPULATE
> - /* NB: MAP_POPULATE won't exhaustively alloc all phys pages in the case
> - * MAP_PRIVATE is requested. For mem_prealloc we mmap as MAP_SHARED
> - * to sidestep this quirk.
> - */
> - flags = mem_prealloc ? MAP_POPULATE | MAP_SHARED : MAP_PRIVATE;
> - area = mmap(0, memory, PROT_READ | PROT_WRITE, flags, fd, 0);
> -#else
> area = mmap(0, memory, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0);
> -#endif
> if (area == MAP_FAILED) {
> perror("file_ram_alloc: can't mmap RAM pages");
> close(fd);
> return (NULL);
> }
> +
> + if (mem_prealloc) {
> + int ret, i;
> + struct sigaction act, oldact;
> + sigset_t set, oldset;
> +
> + memset(&act, 0, sizeof(act));
> + act.sa_handler = &sigbus_handler;
> + act.sa_flags = 0;
> +
> + ret = sigaction(SIGBUS, &act, &oldact);
> + if (ret) {
> + perror("file_ram_alloc: fail to install signal handler");
> + exit(1);
> + }
> +
> + /* unblock SIGBUS */
> + pthread_sigmask(SIG_BLOCK, NULL, &oldset);
This is not needed, just pass &oldset in the SIG_UNBLOCK call below.
> + sigemptyset(&set);
> + sigaddset(&set, SIGBUS);
> + pthread_sigmask(SIG_UNBLOCK, &set, NULL);
> +
> + if (sigsetjmp(sigjump, 1)) {
> + fprintf(stderr, "file_ram_alloc: failed to preallocate pages\n");
> + exit(1);
> + }
> +
> + /* MAP_POPULATE silently ignores failures */
> + for (i = 0; i < (memory/hpagesize)-1; i++) {
> + memset(area + (hpagesize*i), 0, 1);
> + }
> +
> + ret = sigaction(SIGBUS, &oldact, NULL);
> + if (ret) {
> + perror("file_ram_alloc: fail to reinstall signal handler");
> + exit(1);
> + }
> +
> + if (sigismember(&oldset, SIGBUS)) {
> + sigemptyset(&set);
> + sigaddset(&set, SIGBUS);
> + pthread_sigmask(SIG_BLOCK, &set, NULL);
> + }
Just use SIG_SETMASK with oldset, unconditionally.
Ok with these changes.
Paolo
> + }
> +
> block->fd = fd;
> return area;
> }
> Index: qemu/vl.c
> ===================================================================
> --- qemu.orig/vl.c
> +++ qemu/vl.c
> @@ -188,9 +188,7 @@ static int display_remote;
> const char* keyboard_layout = NULL;
> ram_addr_t ram_size;
> const char *mem_path = NULL;
> -#ifdef MAP_POPULATE
> int mem_prealloc = 0; /* force preallocation of physical target memory */
> -#endif
> int nb_nics;
> NICInfo nd_table[MAX_NICS];
> int autostart;
> @@ -3205,11 +3203,9 @@ int main(int argc, char **argv, char **e
> case QEMU_OPTION_mempath:
> mem_path = optarg;
> break;
> -#ifdef MAP_POPULATE
> case QEMU_OPTION_mem_prealloc:
> mem_prealloc = 1;
> break;
> -#endif
> case QEMU_OPTION_d:
> log_mask = optarg;
> break;
> Index: qemu/qemu-options.def
> ===================================================================
> --- qemu.orig/qemu-options.def
> +++ qemu/qemu-options.def
> @@ -66,11 +66,9 @@ stringify(DEFAULT_RAM_SIZE) "]\n", QEMU_
> DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
> "-mem-path FILE provide backing storage for guest RAM\n", QEMU_ARCH_ALL)
>
> -#ifdef MAP_POPULATE
> DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
> "-mem-prealloc preallocate guest memory (use with -mem-path)\n",
> QEMU_ARCH_ALL)
> -#endif
>
> DEF("k", HAS_ARG, QEMU_OPTION_k,
> "-k language use keyboard layout (for example 'fr' for French)\n",
> Index: git/qemu/qemu-options.hx
> ===================================================================
> --- qemu.orig/qemu-options.hx
> +++ qemu/qemu-options.hx
> @@ -228,7 +228,6 @@ STEXI
> Allocate guest RAM from a temporarily created file in @var{path}.
> ETEXI
>
> -#ifdef MAP_POPULATE
> DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc,
> "-mem-prealloc preallocate guest memory (use with -mem-path)\n",
> QEMU_ARCH_ALL)
> @@ -237,7 +236,6 @@ STEXI
> @findex -mem-prealloc
> Preallocate memory when using -mem-path.
> ETEXI
> -#endif
>
> DEF("k", HAS_ARG, QEMU_OPTION_k,
> "-k language use keyboard layout (for example 'fr' for French)\n",
>
>
>
>
- [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Marcelo Tosatti, 2013/10/07
- [Qemu-devel] [patch 2/2] qemu: add -mem-path-force option to force RAM allocation via -mem-path, Marcelo Tosatti, 2013/10/07
- [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Marcelo Tosatti, 2013/10/07
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Paolo Bonzini, 2013/10/08
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Marcelo Tosatti, 2013/10/08
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Paolo Bonzini, 2013/10/09
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Marcelo Tosatti, 2013/10/09
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Paolo Bonzini, 2013/10/09
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Paolo Bonzini, 2013/10/10
- Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Marcelo Tosatti, 2013/10/10
Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually,
Paolo Bonzini <=
Re: [Qemu-devel] [patch 1/2] qemu: mempath: prefault pages manually, Peter Maydell, 2013/10/28
Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Markus Armbruster, 2013/10/08
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Paolo Bonzini, 2013/10/08
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Marcelo Tosatti, 2013/10/08
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Markus Armbruster, 2013/10/09
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Marcelo Tosatti, 2013/10/09
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Paolo Bonzini, 2013/10/09
- Re: [Qemu-devel] [patch 0/2] force -mem-path RAM allocation, Marcelo Tosatti, 2013/10/10