[Crash-utility] [PATCH] Speed up usage of a flat makedumpfile vmcore.

[Dave Anderson]

----- Original Message -----
> Using a bubble sort is slow, switch to an insertion sort.
> 
> bubble sort:     real    3m45.168s
> 
> insertion sort:  real    0m3.164s
> 
> Signed-off-by: Don Slutz <dslutz at verizon.com>
> ---
> I do have a big (32G sized file, that gzipped is 357M).
> let me know if you want it.

Hi Don,

I'm running some sanity tests with a couple 94GB flat vmcores by comparing
the data output of some of the more verbose commands.  But upon invocation,
I do see some significant speed increases, for example:

  vmcore.1  2m45.545s  ->  1m31.428s 
  vmcore.2  2m42.806s  ->  0m46.624s

The numbers change from invocation to invocation, but always in the 
same direction.  Probably file page caching is affecting the times.

Anyway, I've never taken the time to actually understand how the flat format
is laid out, and I would normally ask the author to sign off on any major
changes to it.  But I see that Ken'ichi Ohmichi is no longer a member
of this list, so for all practical purposes, it's currently "unmaintained".
I'll continue testing further tomorrow, but if by chance you can whip up a 
simplified explanation of the flat dumpfile layout, I'd appreciate it.

Thanks,
  Dave


> It is the same as the xen rename of dom0
> 
>  makedumpfile.c | 56 +++++++++++++++++++++++++-------------------------------
>  1 file changed, 25 insertions(+), 31 deletions(-)
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index f6834b9..c76e22c 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -56,8 +56,10 @@ store_flat_data_array(char *file, struct flat_data **fda)
>  {
>  	int			result = FALSE, fd;
>  	int64_t			offset_fdh;
> +	int64_t			offset_report = 0;
>  	unsigned long long	num_allocated = 0;
>  	unsigned long long	num_stored    = 0;
> +	unsigned long long	sort_idx;
>  	unsigned long long	size_allocated;
>  	struct flat_data	*ptr = NULL, *cur, *new;
>  	struct makedumpfile_data_header	fdh;
> @@ -100,11 +102,34 @@ store_flat_data_array(char *file, struct flat_data
> **fda)
>  			break;
>  		}
>  		cur = ptr + num_stored;
> +		sort_idx = num_stored;
> +		while (sort_idx) {
> +			new = ptr + --sort_idx;
> +			if (new->off_rearranged >= fdh.offset) {
> +				cur->off_flattened = new->off_flattened;
> +				cur->off_rearranged = new->off_rearranged;
> +				cur->buf_size = new->buf_size;
> +				cur = new;
> +			} else {
> +				if (CRASHDEBUG(1) && sort_idx + 1 != num_stored) {
> +					fprintf(fp,
> +						"makedumpfile: Moved from %lld to %lld\n",
> +						num_stored, sort_idx + 1);
> +				}
> +				break;
> +			}
> +		}
>  		cur->off_flattened  = offset_fdh + sizeof(fdh);
>  		cur->off_rearranged = fdh.offset;
>  		cur->buf_size       = fdh.buf_size;
>  		num_stored++;
>  
> +		if (CRASHDEBUG(1) && (fdh.offset >> 30) > (offset_report >> 30)) {
> +			fprintf(fp, "makedumpfile: At %lld GiB\n",
> +			      fdh.offset >> 30);
> +			offset_report = fdh.offset;
> +		}
> +
>  		/* seek for next makedumpfile_data_header. */
>  		if (lseek(fd, fdh.buf_size, SEEK_CUR) < 0) {
>  			error(INFO, "%s: seek error (flat format)\n", file);
> @@ -121,35 +146,6 @@ store_flat_data_array(char *file, struct flat_data
> **fda)
>  	return num_stored;
>  }
>  
> -static void
> -sort_flat_data_array(struct flat_data **fda, unsigned long long num_fda)
> -{
> -	unsigned long long	i, j;
> -	struct flat_data	tmp, *cur_i, *cur_j;
> -
> -	for (i = 0; i < num_fda - 1; i++) {
> -		for (j = i + 1; j < num_fda; j++) {
> -			cur_i = *fda + i;
> -			cur_j = *fda + j;
> -
> -			if (cur_i->off_rearranged < cur_j->off_rearranged)
> -				continue;
> -
> -			tmp.off_flattened  = cur_i->off_flattened;
> -			tmp.off_rearranged = cur_i->off_rearranged;
> -			tmp.buf_size       = cur_i->buf_size;
> -
> -			cur_i->off_flattened  = cur_j->off_flattened;
> -			cur_i->off_rearranged = cur_j->off_rearranged;
> -			cur_i->buf_size       = cur_j->buf_size;
> -
> -			cur_j->off_flattened  = tmp.off_flattened;
> -			cur_j->off_rearranged = tmp.off_rearranged;
> -			cur_j->buf_size       = tmp.buf_size;
> -		}
> -	}
> -}
> -
>  static int
>  read_all_makedumpfile_data_header(char *file)
>  {
> @@ -161,8 +157,6 @@ read_all_makedumpfile_data_header(char *file)
>  	if (retval < 0)
>  		return FALSE;
>  
> -	sort_flat_data_array(&fda, num);
> -
>  	afd.num_array = num;
>  	afd.array     = fda;
>  
> --
> 1.8.4
> 
>