Re: [PATCH v2] diskdump: Optimize the boot time

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-----Original Message-----
> 1.) The vmcore file maybe very big.
> 
>     For example, I have a vmcore file which is over 23G,
>     and the panic kernel had 767.6G memory,
>     its max_sect_len is 4468736.

4468736 * 4096 * 4k -> about 68T.  Apparently there are systems that can
have a large physical space (max_mapnr) comparing with its actual memory.

anyway, thanks for the huge improvement.  The v2 patch looks good to me.

Acked-by: Kazuhito Hagio <k-hagio-ab@xxxxxxx>

Thanks,
Kazu



> 
>     Current code costs too much time to do the following loop:
>     ..............................................
>  	for (i = 1; i < max_sect_len + 1; i++) {
>  		dd->valid_pages[i] = dd->valid_pages[i - 1];
> 		for (j = 0; j < BITMAP_SECT_LEN; j++, pfn++)
> 			if (page_is_dumpable(pfn))
> 				dd->valid_pages[i]++;
>     ..............................................
> 
>     For my case, it costs about 56 seconds to finish the
>     big loop.
> 
>     This patch moves the hweightXX macros to defs.h,
>     and uses hweight64 to optimize the loop.
> 
>     For my vmcore, the loop only costs about one second now.
> 
> 2.) Tests result:
>   # cat ./commands.txt
>       quit
> 
>  Before:
> 
>   #echo  3 > /proc/sys/vm/drop_caches;
>   #time ./crash -i ./commands.txt /root/t/vmlinux /root/t/vmcore > /dev/null 2>&1
>    ............................
> 	real    1m54.259s
> 	user    1m12.494s
> 	sys     0m3.857s
>    ............................
> 
>  After this patch:
> 
>   #echo  3 > /proc/sys/vm/drop_caches;
>   #time ./crash -i ./commands.txt /root/t/vmlinux /root/t/vmcore > /dev/null 2>&1
>    ............................
> 	real    0m55.217s
> 	user    0m15.114s
> 	sys     0m3.560s
>    ............................
> 
> Signed-off-by: Huang Shijie <shijie@xxxxxxxxxxxxxxxxxxxxxx>
> ---
> v1 --> v2:
> 	1.) change u64 to ulonglong.
> 	2.) compile this patch in x86_64.
> 
> ---
>  defs.h     | 20 ++++++++++++++++++++
>  diskdump.c | 12 +++++++++---
>  sbitmap.c  | 19 -------------------
>  3 files changed, 29 insertions(+), 22 deletions(-)
> 
> diff --git a/defs.h b/defs.h
> index 81ac049..1e8360d 100644
> --- a/defs.h
> +++ b/defs.h
> @@ -4531,6 +4531,26 @@ struct machine_specific {
>  #define NUM_IN_BITMAP(bitmap, x) (bitmap[(x)/BITS_PER_LONG] & NUM_TO_BIT(x))
>  #define SET_BIT(bitmap, x) (bitmap[(x)/BITS_PER_LONG] |= NUM_TO_BIT(x))
> 
> +static inline unsigned int __const_hweight8(unsigned long w)
> +{
> +	return
> +		(!!((w) & (1ULL << 0))) +
> +		(!!((w) & (1ULL << 1))) +
> +		(!!((w) & (1ULL << 2))) +
> +		(!!((w) & (1ULL << 3))) +
> +		(!!((w) & (1ULL << 4))) +
> +		(!!((w) & (1ULL << 5))) +
> +		(!!((w) & (1ULL << 6))) +
> +		(!!((w) & (1ULL << 7)));
> +}
> +
> +#define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w)  >> 8))
> +#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
> +#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
> +
> +#define hweight32(w) __const_hweight32(w)
> +#define hweight64(w) __const_hweight64(w)
> +
>  /*
>   *  precision lengths for fprintf
>   */
> diff --git a/diskdump.c b/diskdump.c
> index d567427..ff1e9a3 100644
> --- a/diskdump.c
> +++ b/diskdump.c
> @@ -547,6 +547,7 @@ read_dump_header(char *file)
>  	ulong pfn;
>  	int i, j, max_sect_len;
>  	int is_split = 0;
> +	ulonglong tmp, *bitmap;
> 
>  	if (block_size < 0)
>  		return FALSE;
> @@ -899,11 +900,16 @@ restart:
> 
>  	dd->valid_pages = calloc(sizeof(ulong), max_sect_len + 1);
>  	dd->max_sect_len = max_sect_len;
> +
> +	/* It is safe to convert it to (ulonglong *). */
> +	bitmap = (ulonglong *)dd->dumpable_bitmap;
>  	for (i = 1; i < max_sect_len + 1; i++) {
>  		dd->valid_pages[i] = dd->valid_pages[i - 1];
> -		for (j = 0; j < BITMAP_SECT_LEN; j++, pfn++)
> -			if (page_is_dumpable(pfn))
> -				dd->valid_pages[i]++;
> +		for (j = 0; j < BITMAP_SECT_LEN; j += 64, pfn += 64) {
> +			tmp = bitmap[pfn >> 6];
> +			if (tmp)
> +				dd->valid_pages[i] += hweight64(tmp);
> +		}
>  	}
> 
>          return TRUE;
> diff --git a/sbitmap.c b/sbitmap.c
> index 286259f..96a61e6 100644
> --- a/sbitmap.c
> +++ b/sbitmap.c
> @@ -49,25 +49,6 @@ struct sbitmapq_data {
> 
>  static uint sb_flags = 0;
> 
> -static inline unsigned int __const_hweight8(unsigned long w)
> -{
> -	return
> -		(!!((w) & (1ULL << 0))) +
> -		(!!((w) & (1ULL << 1))) +
> -		(!!((w) & (1ULL << 2))) +
> -		(!!((w) & (1ULL << 3))) +
> -		(!!((w) & (1ULL << 4))) +
> -		(!!((w) & (1ULL << 5))) +
> -		(!!((w) & (1ULL << 6))) +
> -		(!!((w) & (1ULL << 7)));
> -}
> -
> -#define __const_hweight16(w) (__const_hweight8(w)  + __const_hweight8((w)  >> 8))
> -#define __const_hweight32(w) (__const_hweight16(w) + __const_hweight16((w) >> 16))
> -#define __const_hweight64(w) (__const_hweight32(w) + __const_hweight32((w) >> 32))
> -
> -#define hweight32(w) __const_hweight32(w)
> -#define hweight64(w) __const_hweight64(w)
> 
>  #define BIT(nr)			(1UL << (nr))
> 
> --
> 2.30.2

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