Re: makedumpfile memmory usage seems high with option -E

[Arthur Zou <zzou@redhat.com>]

----- Original Message -----
> Hello Vivek,
> 
> >Hi Atsushi/Hatayama,
> >
> >We noticed in our testing that makedumpfile gets OOM killed if we happen
> >to use -E option. Saving to compressed kdump format works just fine.
> >
> >Also we noticed that with -E if we disable cyclic mode then it works just
> >fine.
> >
> >So looks like something is going on with -E and cyclic mode enabled. I am
> >not sure what it is.
> >
> >Do you suspect something?
> 
> At first, I supposed the function to calculate cyclic buffer size may
> be related to this issue, but I haven't found the answer yet...
> 
> int
> calculate_cyclic_buffer_size() {
> 
>         if (info->flag_elf_dumpfile) {
>                 free_size = get_free_memory_size() * 0.4;
>                 needed_size = (info->max_mapnr * 2) / BITPERBYTE;
>         } else {
>                 free_size = get_free_memory_size() * 0.8;
>                 needed_size = info->max_mapnr / BITPERBYTE;
>         }
>         [...]
>         info->bufsize_cyclic = (free_size <= needed_size) ? free_size :
>         needed_size;
> 
> 
> I've found this function has an issue about memory allocation.
> When -E is specified, info->bufsize_cyclic will be the total size of
> the 1st and 2nd bitmap if free memory is enough. Then,
> info->bufsize_cyclic will be used to allocate each bitmap in
> prepare_bitmap_buffer_cyclic() like below:
> 
>         if ((info->partial_bitmap1 = (char *)malloc(info->bufsize_cyclic)) ==
>         NULL) {
>                 ERRMSG("Can't allocate memory for the 1st-bitmap. %s\n",
>                        strerror(errno));
>                 return FALSE;
>         }
>         if ((info->partial_bitmap2 = (char *)malloc(info->bufsize_cyclic)) ==
>         NULL) {
>                 ERRMSG("Can't allocate memory for the 2nd-bitmap. %s\n",
>                        strerror(errno));
>                 return FALSE;
>         }
> 
> It's a too much allocation definitely, but it mustn't exceed 80% of free
> memory due to the condition check in calculate_cyclic_buffer_size(), so
> I think the OOM issue will not happen by this issue.
> I'll fix this too much allocation with the patch below, but it will not
> resolve your OOM issue...
> 
> BTW, what are your version of makedumpfile and crashkernel= size and
> the system memory size? and does the issue happen even if you specify
> --cyclic-buffer which is small enough to fit the available memory ?
> I'm curious to know the details of the condition which cause the issue.
> 
> 

Hi Atsushi Kumagai
   The makedumpfile version is 1.5.4. crashkernel=auto which actually is 166M.
the system memory size is about 96G and the arch is x86_64 which kernel version
3.10.110. But the same issue happened when using the newest makedumpfile in devel
branch. After add --cyclic-buffer=100, dump succeed.

Thanks
arthur 

> Thanks
> Atsushi Kumagai
> 
> 
> diff --git a/makedumpfile.c b/makedumpfile.c
> index 75092a8..ae9e69a 100644
> --- a/makedumpfile.c
> +++ b/makedumpfile.c
> @@ -8996,7 +8996,7 @@ out:
>   */
>  int
>  calculate_cyclic_buffer_size(void) {
> -	unsigned long long free_size, needed_size;
> +	unsigned long long limit_size, bitmap_size;
>  
>  	if (info->max_mapnr <= 0) {
>  		ERRMSG("Invalid max_mapnr(%llu).\n", info->max_mapnr);
> @@ -9009,18 +9009,17 @@ calculate_cyclic_buffer_size(void) {
>  	 * within 80% of free memory.
>  	 */
>  	if (info->flag_elf_dumpfile) {
> -		free_size = get_free_memory_size() * 0.4;
> -		needed_size = (info->max_mapnr * 2) / BITPERBYTE;
> +		limit_size = get_free_memory_size() * 0.4;
>  	} else {
> -		free_size = get_free_memory_size() * 0.8;
> -		needed_size = info->max_mapnr / BITPERBYTE;
> +		limit_size = get_free_memory_size() * 0.8;
>  	}
> +	bitmap_size = info->max_mapnr / BITPERBYTE;
>  
>  	/* if --split was specified cyclic buffer allocated per dump file */
>  	if (info->num_dumpfile > 1)
> -		needed_size /= info->num_dumpfile;
> +		bitmap_size /= info->num_dumpfile;
>  
> -	info->bufsize_cyclic = (free_size <= needed_size) ? free_size :
> needed_size;
> +	info->bufsize_cyclic = (limit_size <= bitmap_size) ? limit_size :
> bitmap_size;
>  
>  	return TRUE;
>  }
> --
> 1.8.0.2
> 
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