Re: [PATCH] makedumpfile: shorten cyclic exclude-unnecessary passes

[HATAYAMA Daisuke <d.hatayama@jp.fujitsu.com>]

(2013/08/29 7:08), Cliff Wickman wrote:
> From: Cliff Wickman <cpw@sgi.com>
> 
> - get_mm_sparsemem(): reduce the number of entries in the mem_map[] by
>    recording only those sections which actually exist in memory

I have missed this point. How much does this change speed up?

In general, if you want to say your patch improves performance, it's better to
demonstrate it in a measurable way such as benchmark.

> - shorten the executions of __exclude_unnecessary_pages() by passing it only
>    the pfn's of the current cyclic area
> 

I did try to similar kind of effort some months ago locally to figure out where
to improve cyclic-mode. In case of me, I noticed possibility of unnecessary processing
being performed out side the area of current cycle from the sanity check below:

int
set_bitmap_cyclic(char *bitmap, unsigned long long pfn, int val)
{
        int byte, bit;

        if (pfn < info->cyclic_start_pfn || info->cyclic_end_pfn <= pfn)
                return FALSE;
<cut>

However, I didn't get distinguishable difference at that time. I ran the program
relatively ordinary class of system with some gigabyte memory so I might not got
distinguishable improvement.

Anyway, I thought it was permissible at that time and I didn't continue that work more.

But these days I have a machine with huge physical memory holes and on that system
this improvement sounds work well. So I much want to try to benchmark this direction
of your improvement patch set.

-- 
Thanks.
HATAYAMA, Daisuke


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