Re: [MAKDUMPFILE PATCH] Add option to estimate the size of vmcore dump files

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Hello Julien,

Thanks for the patch. Some nitpicks inline:

On Mon, Oct 12, 2020 at 12:39 PM Julien Thierry <jthierry@xxxxxxxxxx> wrote:
>
> A user might want to know how much space a vmcore file will take on
> the system and how much space on their disk should be available to
> save it during a crash.
>
> The option --vmcore-size does not create the vmcore file but provides
> an estimation of the size of the final vmcore file created with the
> same make dumpfile options.
>
> Signed-off-by: Julien Thierry <jthierry@xxxxxxxxxx>
> Cc: Kazuhito Hagio <k-hagio-ab@xxxxxxx>
> ---
>  makedumpfile.c | 98 ++++++++++++++++++++++++++++++++++++++++++++++++--
>  makedumpfile.h | 12 +++++++
>  print_info.c   |  4 +++
>  3 files changed, 111 insertions(+), 3 deletions(-)

Please update 'makedumpfile.8' as well in v2, so that the man page can
document the newly added option and how to use it to determine the
vmcore-size.

> diff --git a/makedumpfile.c b/makedumpfile.c
> index 4c4251e..0a2bfba 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -26,6 +26,7 @@
>  #include <limits.h>
>  #include <assert.h>
>  #include <zlib.h>
> +#include <libgen.h>

I know we don't follow alphabetical order for include files in
makedumpfile code, but it would be good to place the new - ones
accordingly. So <libgen.h> can go with <limits.h> here.

>  struct symbol_table    symbol_table;
>  struct size_table      size_table;
> @@ -1366,7 +1367,25 @@ open_dump_file(void)
>         if (!info->flag_force)
>                 open_flags |= O_EXCL;
>
> -       if (info->flag_flatten) {
> +       if (info->flag_vmcore_size) {
> +               char *namecpy;
> +               struct stat statbuf;
> +               int res;
> +
> +               namecpy = strdup(info->name_dumpfile ?
> +                                info->name_dumpfile : ".");
> +
> +               res = stat(dirname(namecpy), &statbuf);
> +               free(namecpy);
> +               if (res != 0)
> +                       return FALSE;
> +
> +               fd = -1;
> +               info->dumpsize_info.blksize = statbuf.st_blksize;
> +               info->dumpsize_info.block_buff_size = BASE_NUM_BLOCKS;
> +               info->dumpsize_info.block_info = calloc(BASE_NUM_BLOCKS, 1);
> +               info->dumpsize_info.non_hole_blocks = 0;
> +       } else if (info->flag_flatten) {
>                 fd = STDOUT_FILENO;
>                 info->name_dumpfile = filename_stdout;
>         } else if ((fd = open(info->name_dumpfile, open_flags,
> @@ -1384,6 +1403,9 @@ check_dump_file(const char *path)
>  {
>         char *err_str;
>
> +       if (info->flag_vmcore_size)
> +               return TRUE;
> +
>         if (access(path, F_OK) != 0)
>                 return TRUE; /* File does not exist */
>         if (info->flag_force) {
> @@ -4622,6 +4644,47 @@ write_and_check_space(int fd, void *buf, size_t buf_size, char *file_name)
>         return TRUE;
>  }
>
> +static int
> +write_buffer_update_size_info(off_t offset, void *buf, size_t buf_size)
> +{
> +       struct dumpsize_info *dumpsize_info = &info->dumpsize_info;
> +       int blk_end_idx = (offset + buf_size - 1) / dumpsize_info->blksize;
> +       int i;
> +
> +       /* Need to grow the dumpsize block buffer? */
> +       if (blk_end_idx >= dumpsize_info->block_buff_size) {
> +               int alloc_size = MAX(blk_end_idx - dumpsize_info->block_buff_size, BASE_NUM_BLOCKS);
> +
> +               dumpsize_info->block_info = realloc(dumpsize_info->block_info,
> +                                                   dumpsize_info->block_buff_size + alloc_size);
> +               if (!dumpsize_info->block_info) {
> +                       ERRMSG("Not enough memory\n");
> +                       return FALSE;
> +               }
> +
> +               memset(dumpsize_info->block_info + dumpsize_info->block_buff_size,
> +                      0, alloc_size);
> +               dumpsize_info->block_buff_size += alloc_size;
> +       }
> +
> +       for (i = 0; i < buf_size; ++i) {
> +               int blk_idx = (offset + i) / dumpsize_info->blksize;
> +
> +               if (dumpsize_info->block_info[blk_idx]) {
> +                       i += dumpsize_info->blksize;
> +                       i = i - (i % dumpsize_info->blksize) - 1;
> +                       continue;
> +               }
> +
> +               if (((char *) buf)[i] != 0) {
> +                       dumpsize_info->non_hole_blocks++;
> +                       dumpsize_info->block_info[blk_idx] = 1;
> +               }
> +       }
> +
> +       return TRUE;
> +}
> +
>  int
>  write_buffer(int fd, off_t offset, void *buf, size_t buf_size, char *file_name)
>  {
> @@ -4643,6 +4706,8 @@ write_buffer(int fd, off_t offset, void *buf, size_t buf_size, char *file_name)
>                 }
>                 if (!write_and_check_space(fd, &fdh, sizeof(fdh), file_name))
>                         return FALSE;
> +       } else if (info->flag_vmcore_size && fd == info->fd_dumpfile) {
> +               return write_buffer_update_size_info(offset, buf, buf_size);
>         } else {
>                 if (lseek(fd, offset, SEEK_SET) == failed) {
>                         ERRMSG("Can't seek the dump file(%s). %s\n",
> @@ -9018,6 +9083,12 @@ close_dump_file(void)
>         if (info->flag_flatten)
>                 return;
>
> +       if (info->flag_vmcore_size && info->fd_dumpfile == -1) {
> +               free(info->dumpsize_info.block_info);
> +               info->dumpsize_info.block_info = NULL;
> +               return;
> +       }
> +
>         if (close(info->fd_dumpfile) < 0)
>                 ERRMSG("Can't close the dump file(%s). %s\n",
>                     info->name_dumpfile, strerror(errno));
> @@ -10963,6 +11034,12 @@ check_param_for_creating_dumpfile(int argc, char *argv[])
>         if (info->flag_flatten && info->flag_split)
>                 return FALSE;
>
> +       if (info->flag_flatten && info->flag_vmcore_size)
> +               return FALSE;
> +
> +       if (info->flag_mem_usage && info->flag_vmcore_size)
> +               return FALSE;
> +
>         if (info->name_filterconfig && !info->name_vmlinux)
>                 return FALSE;
>
> @@ -11043,7 +11120,8 @@ check_param_for_creating_dumpfile(int argc, char *argv[])
>                  */
>                 info->name_memory   = argv[optind];
>
> -       } else if ((argc == optind + 1) && info->flag_mem_usage) {
> +       } else if ((argc == optind + 1) && (info->flag_mem_usage ||
> +                                           info->flag_vmcore_size)) {
>                 /*
>                 * Parameter for showing the page number of memory
>                 * in different use from.
> @@ -11423,6 +11501,7 @@ static struct option longopts[] = {
>         {"work-dir", required_argument, NULL, OPT_WORKING_DIR},
>         {"num-threads", required_argument, NULL, OPT_NUM_THREADS},
>         {"check-params", no_argument, NULL, OPT_CHECK_PARAMS},
> +       {"vmcore-size", no_argument, NULL, OPT_VMCORE_SIZE},
>         {0, 0, 0, 0}
>  };
>
> @@ -11589,6 +11668,9 @@ main(int argc, char *argv[])
>                         info->flag_check_params = TRUE;
>                         message_level = DEFAULT_MSG_LEVEL;
>                         break;
> +               case OPT_VMCORE_SIZE:
> +                       info->flag_vmcore_size = TRUE;
> +                       break;
>                 case '?':
>                         MSG("Commandline parameter is invalid.\n");
>                         MSG("Try `makedumpfile --help' for more information.\n");
> @@ -11598,6 +11680,10 @@ main(int argc, char *argv[])
>         if (flag_debug)
>                 message_level |= ML_PRINT_DEBUG_MSG;
>
> +       if (info->flag_vmcore_size)
> +               /* Suppress progress indicator as dumpfile won't get written */
> +               message_level &= ~ML_PRINT_PROGRESS;
> +
>         if (info->flag_check_params)
>                 /* suppress debugging messages */
>                 message_level = DEFAULT_MSG_LEVEL;
> @@ -11751,7 +11837,11 @@ main(int argc, char *argv[])
>                         goto out;
>
>                 MSG("\n");
> -               if (info->flag_split) {
> +
> +               if (info->flag_vmcore_size) {
> +                       MSG("Estimated size to save vmcore is: %lld Bytes\n",
> +                           (long long)info->dumpsize_info.non_hole_blocks * info->dumpsize_info.blksize);
> +               } else if (info->flag_split) {
>                         MSG("The dumpfiles are saved to ");
>                         for (i = 0; i < info->num_dumpfile; i++) {
>                                 if (i != (info->num_dumpfile - 1))
> @@ -11808,6 +11898,8 @@ out:
>                         free(info->page_buf);
>                 if (info->parallel_info != NULL)
>                         free(info->parallel_info);
> +               if (info->dumpsize_info.block_info != NULL)
> +                       free(info->dumpsize_info.block_info);
>                 free(info);
>
>                 if (splitblock) {
> diff --git a/makedumpfile.h b/makedumpfile.h
> index 03fb4ce..fd78d5f 100644
> --- a/makedumpfile.h
> +++ b/makedumpfile.h
> @@ -1277,6 +1277,15 @@ struct parallel_info {
>  #endif
>  };
>
> +#define BASE_NUM_BLOCKS        50
> +
> +struct dumpsize_info {
> +       int blksize;
> +       int block_buff_size;
> +       unsigned char *block_info;
> +       int non_hole_blocks;
> +};
> +
>  struct ppc64_vmemmap {
>         unsigned long           phys;
>         unsigned long           virt;
> @@ -1321,6 +1330,7 @@ struct DumpInfo {
>         int             flag_vmemmap;        /* kernel supports vmemmap address space */
>         int             flag_excludevm;      /* -e - excluding unused vmemmap pages */
>         int             flag_use_count;      /* _refcount is named _count in struct page */
> +       int             flag_vmcore_size;    /* estimate the size of the vmcore file instead of creating it */
>         unsigned long   vaddr_for_vtop;      /* virtual address for debugging */
>         long            page_size;           /* size of page */
>         long            page_shift;
> @@ -1425,6 +1435,7 @@ struct DumpInfo {
>         int                     num_dumpfile;
>         struct splitting_info   *splitting_info;
>         struct parallel_info    *parallel_info;
> +       struct dumpsize_info    dumpsize_info;
>
>         /*
>          * bitmap info:
> @@ -2364,6 +2375,7 @@ struct elf_prstatus {
>  #define OPT_NUM_THREADS         OPT_START+16
>  #define OPT_PARTIAL_DMESG       OPT_START+17
>  #define OPT_CHECK_PARAMS        OPT_START+18
> +#define OPT_VMCORE_SIZE         OPT_START+19
>
>  /*
>   * Function Prototype.
> diff --git a/print_info.c b/print_info.c
> index e0c38b4..6f5a165 100644
> --- a/print_info.c
> +++ b/print_info.c
> @@ -308,6 +308,10 @@ print_usage(void)
>         MSG("      the crashkernel range, then calculates the page number of different kind per\n");
>         MSG("      vmcoreinfo. So currently /proc/kcore need be specified explicitly.\n");
>         MSG("\n");
> +       MSG("  [--vmcore-size]:\n");
> +       MSG("      This option provides an estimation of the size needed to save VMCORE on disk.\n");
> +       MSG("      This option option cannot be used in combination with -F.\n");

Also not in combination with --mem-usage (as per the code changes above)?
And may be the options '--mem-usage / -F' also need an update to
mention they can't be used with --vmcore-size option.

> +       MSG("\n");
>         MSG("  [-D]:\n");
>         MSG("      Print debugging message.\n");
>         MSG("\n");
> --

I like the idea, but sometimes we use makedumpfile to generate a
dumpfile in the primary kernel as well. For example:

$ makedumpfile -d 31 -x vmlinux /proc/kcore dumpfile

In such use-cases it is useful to use --vmcore-size and still generate
the dumpfile (right now the default behaviour is not to generate a
dumpfile when --vmcore-size is specified). Maybe we need to think more
on supporting this use-case as well.

Regards,
Bhupesh


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