Jason Baron <jba...@redhat.com> writes:
> Add a new '[,dump=on|off]' option to the '-m' memory option. When 'dump=off'
> is specified, guest memory is omitted from the core dump. The default behavior
> continues to be to include guest memory when a core dump is triggered. In my
> testing, this brought the core dump size down from 384MB to 6 MB on a 2GB
> guest.
> Thanks to Avi Kivity for the command line syntax.
>
> Signed-off-by: Jason Baron <jba...@redhat.com>
> ---
> exec.c | 13 +++++++++++++
> osdep.h | 7 +++++++
> qemu-options.hx | 11 +++++++----
> sysemu.h | 1 +
> vl.c | 51 +++++++++++++++++++++++++++++++++++----------------
> 5 files changed, 63 insertions(+), 20 deletions(-)
>
> diff --git a/exec.c b/exec.c
> index feb4795..75b8e23 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -35,6 +35,7 @@
> #include "qemu-timer.h"
> #include "memory.h"
> #include "exec-memory.h"
> +#include "sysemu.h"
> #if defined(CONFIG_USER_ONLY)
> #include <qemu.h>
> #if defined(__FreeBSD__) || defined(__FreeBSD_kernel__)
> @@ -2514,6 +2515,7 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size,
> void *host,
> MemoryRegion *mr)
> {
> RAMBlock *new_block;
> + int ret;
>
> size = TARGET_PAGE_ALIGN(size);
> new_block = g_malloc0(sizeof(*new_block));
> @@ -2555,6 +2557,17 @@ ram_addr_t qemu_ram_alloc_from_ptr(ram_addr_t size,
> void *host,
> last_ram_offset() >>
> TARGET_PAGE_BITS);
> cpu_physical_memory_set_dirty_range(new_block->offset, size, 0xff);
>
> +
> + /* Use MADV_DONTDUMP, if user doesn't want the guest memory in the core
> */
> + if (dont_dump_guest) {
> + ret = qemu_madvise(new_block->host, size, QEMU_MADV_DONTDUMP);
> + if (ret) {
> + perror("qemu_madvise");
> + fprintf(stderr, "madvise doesn't support MADV_DONTDUMP, "
> + "but dump=off specified\n");
> + }
> + }
> +
> if (kvm_enabled())
> kvm_setup_guest_memory(new_block->host, size);
>
> diff --git a/osdep.h b/osdep.h
> index 1e15a4b..e2d0f57 100644
> --- a/osdep.h
> +++ b/osdep.h
> @@ -102,6 +102,11 @@ void qemu_vfree(void *ptr);
> #else
> #define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
> #endif
> +#ifdef MADV_DONTDUMP
> +#define QEMU_MADV_DONTDUMP MADV_DONTDUMP
> +#else
> +#define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID
> +#endif
>
> #elif defined(CONFIG_POSIX_MADVISE)
>
> @@ -109,6 +114,7 @@ void qemu_vfree(void *ptr);
> #define QEMU_MADV_DONTNEED POSIX_MADV_DONTNEED
> #define QEMU_MADV_DONTFORK QEMU_MADV_INVALID
> #define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
> +#define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID
>
> #else /* no-op */
>
> @@ -116,6 +122,7 @@ void qemu_vfree(void *ptr);
> #define QEMU_MADV_DONTNEED QEMU_MADV_INVALID
> #define QEMU_MADV_DONTFORK QEMU_MADV_INVALID
> #define QEMU_MADV_MERGEABLE QEMU_MADV_INVALID
> +#define QEMU_MADV_DONTDUMP QEMU_MADV_INVALID
>
> #endif
>
> diff --git a/qemu-options.hx b/qemu-options.hx
> index dc68e15..9c21b99 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -382,14 +382,17 @@ the write back by pressing @key{C-a s}
> (@pxref{disk_images}).
> ETEXI
>
> DEF("m", HAS_ARG, QEMU_OPTION_m,
> - "-m megs set virtual RAM size to megs MB [default="
> - stringify(DEFAULT_RAM_SIZE) "]\n", QEMU_ARCH_ALL)
> + "-m megs[,dump=on|off]\n"
> + " set virtual RAM size to megs MB [default="
> stringify(DEFAULT_RAM_SIZE) "]\n"
> + " use 'dump=off' to omit guest memory from a core dump
> [default=on]\n",
> + QEMU_ARCH_ALL)
> STEXI
> -@item -m @var{megs}
> +@item -m @var{megs}[,dump=on|off]
> @findex -m
> Set virtual RAM size to @var{megs} megabytes. Default is 128 MiB.
> Optionally,
> a suffix of ``M'' or ``G'' can be used to signify a value in megabytes or
> -gigabytes respectively.
> +gigabytes respectively. When 'dump=off' is specified, the guest memory is
> omitted
> +from a qemu core dump. The default is 'dump=on'.
> ETEXI
>
> DEF("mem-path", HAS_ARG, QEMU_OPTION_mempath,
> diff --git a/sysemu.h b/sysemu.h
> index 6540c79..f1a6f08 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -132,6 +132,7 @@ extern uint8_t *boot_splash_filedata;
> extern int boot_splash_filedata_size;
> extern uint8_t qemu_extra_params_fw[2];
> extern QEMUClock *rtc_clock;
> +extern int dont_dump_guest;
>
> #define MAX_NODES 64
> extern int nb_numa_nodes;
> diff --git a/vl.c b/vl.c
> index c18bb80..54ff314 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -226,6 +226,7 @@ int boot_menu;
> uint8_t *boot_splash_filedata;
> int boot_splash_filedata_size;
> uint8_t qemu_extra_params_fw[2];
> +int dont_dump_guest;
>
> typedef struct FWBootEntry FWBootEntry;
>
> @@ -1041,6 +1042,38 @@ static void smp_parse(const char *optarg)
> max_cpus = smp_cpus;
> }
>
> +static void memory_parse(const char *optarg)
> +{
> + char option[128];
> + int64_t value;
> + char *end;
> +
> + optarg = get_opt_name(option, 128, optarg, ',');
> + value = strtosz(option, &end);
> + if (value < 0 || (*end && (*end != ','))) {
> + fprintf(stderr, "qemu: invalid ram size: %s\n", option);
> + exit(1);
> + }
I'll say it before Markus does--we shouldn't open code option parsing
code. This is what QemuOpts is for.
That said, I think this ought to be a -machine option. ram-size is
destined to become a machine option which would make -m N short hand for
-machine ram-size=n anyway.
Otherwise, the patch is nice. I really like MADV_DONTDUMP. We've had
similar requirements in the past and resorted to a really nasty core
dump parser. This is much more elegant.
Regards,
Anthony Liguori
> + if (value != (uint64_t)(ram_addr_t)value) {
> + fprintf(stderr, "qemu: ram size too large\n");
> + exit(1);
> + }
> + ram_size = value;
> + if (*optarg == ',') {
> + optarg++;
> + }
> + if (get_param_value(option, 128, "dump", optarg) != 0) {
> + if (!strcmp(option, "on")) {
> + dont_dump_guest = 0;
> + } else if (!strcmp(option, "off")) {
> + dont_dump_guest = 1;
> + } else {
> + fprintf(stderr, "qemu: invalid option value '%s'\n", option);
> + exit(1);
> + }
> + }
> +}
> +
> /***********************************************************/
> /* USB devices */
>
> @@ -2650,23 +2683,9 @@ int main(int argc, char **argv, char **envp)
> version();
> exit(0);
> break;
> - case QEMU_OPTION_m: {
> - int64_t value;
> - char *end;
> -
> - value = strtosz(optarg, &end);
> - if (value < 0 || *end) {
> - fprintf(stderr, "qemu: invalid ram size: %s\n", optarg);
> - exit(1);
> - }
> -
> - if (value != (uint64_t)(ram_addr_t)value) {
> - fprintf(stderr, "qemu: ram size too large\n");
> - exit(1);
> - }
> - ram_size = value;
> + case QEMU_OPTION_m:
> + memory_parse(optarg);
> break;
> - }
> case QEMU_OPTION_mempath:
> mem_path = optarg;
> break;
> --
> 1.7.1
