>> cyclic mode has to take a two-pass approach for filtering to save on the
>> memory consumption, it's a disadvantage of the cyclic mode and it's basically
>> unavoidable. However, even the cyclic mode can avoid two-pass filtering if free
>> memory space is enough to store the whole 1st and 2nd bitmaps, but the current
>> version doesn't it.
>> The main purpose of this patch set is avoiding that useless filtering,
>> but before that, I merged non-cyclic mode into cyclic mode as code clean up
>> because the codes are almost the same. Instead, I introduce another way to
>> guarantee one-pass filtering by using disk space.
>>
>
>How about compromising progress information to some extent? The first
>pass is intended to count up the exact number of dumpable pages just
>to provide precise progress information. Is such prcision really
>needed?
The first pass counts up the num_dumpable *to calculate the offset of
starting page data region in advance*, otherwise makedumpfile can't start
to write page data except create a sparse file.
7330 write_kdump_pages_and_bitmap_cyclic(struct cache_data *cd_header, struct cache_data *cd_page)
7331 {
7332 struct page_desc pd_zero;
7333 off_t offset_data=0;
7334 struct disk_dump_header *dh = info->dump_header;
7335 unsigned char buf[info->page_size];
7336 struct timeval tv_start;
7337
7338 /*
7339 * Reset counter for debug message.
7340 */
7341 pfn_zero = pfn_cache = pfn_cache_private = 0;
7342 pfn_user = pfn_free = pfn_hwpoison = 0;
7343 pfn_memhole = info->max_mapnr;
7344
7345 cd_header->offset
7346 = (DISKDUMP_HEADER_BLOCKS + dh->sub_hdr_size + dh->bitmap_blocks)
7347 * dh->block_size;
7348 cd_page->offset = cd_header->offset + sizeof(page_desc_t)*info->num_dumpable;
7349 offset_data = cd_page->offset; ^^^^^^^^^^^^
>For example, how about another simple progress information:
>
> pfn / max_mapnr
>
>where pfn is the number of a page frame that is currently
>processed. We know max_mapnr from the beginning, so this is possible
>within one pass. It's less precise but might be precise enough.
I also think it's enough for progress information, but anyway the 1st
pass is necessary as above.
Thanks
Atsushi Kumagai
