"Dr. David Alan Gilbert (git)" <dgilb...@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilb...@redhat.com>
>
> Prior to the start of postcopy, ensure that everything that will
> be transferred later is a whole host-page in size.
>
> This is accomplished by discarding partially transferred host pages
> and marking any that are partially dirty as fully dirty.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilb...@redhat.com>
> + struct RAMBlock *block;
> + unsigned int host_ratio = qemu_host_page_size / TARGET_PAGE_SIZE;
> +
> + if (qemu_host_page_size == TARGET_PAGE_SIZE) {
> + /* Easy case - TPS==HPS - nothing to be done */
> + return 0;
> + }
> +
> + /* Easiest way to make sure we don't resume in the middle of a host-page
> */
> + last_seen_block = NULL;
> + last_sent_block = NULL;
> + last_offset = 0;
It should be enough with the last one, right? if you put
last_seen/sent_block to NULL, you will return from the beggining each
time that you do a migration bitmap sync, penalizing the pages on the
begining of the cycle. Even better than:
last_offset = 0 is doing a:
last_offset &= HOST_PAGE_MASK
or whatever is the constant, no?
> +
> + QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
> + unsigned long first = block->offset >> TARGET_PAGE_BITS;
> + unsigned long len = block->used_length >> TARGET_PAGE_BITS;
> + unsigned long last = first + (len - 1);
> + unsigned long found_set;
> + unsigned long search_start;
next_search? search_next?
> +
> + PostcopyDiscardState *pds =
> + postcopy_discard_send_init(ms, first, block->idstr);
> +
> + /* First pass: Discard all partially sent host pages */
> + found_set = find_next_bit(ms->sentmap, last + 1, first);
> + while (found_set <= last) {
> + bool do_discard = false;
> + unsigned long discard_start_addr;
> + /*
> + * If the start of this run of pages is in the middle of a host
> + * page, then we need to discard this host page.
> + */
> + if (found_set % host_ratio) {
> + do_discard = true;
> + found_set -= found_set % host_ratio;
please, create a PAGE_HOST_ALIGN() macro, or whatever you want to call it?
> + discard_start_addr = found_set;
> + search_start = found_set + host_ratio;
> + } else {
> + /* Find the end of this run */
> + unsigned long found_zero;
> + found_zero = find_next_zero_bit(ms->sentmap, last + 1,
> + found_set + 1);
> + /*
> + * If the 0 isn't at the start of a host page, then the
> + * run of 1's doesn't finish at the end of a host page
> + * and we need to discard.
> + */
> + if (found_zero % host_ratio) {
> + do_discard = true;
> + discard_start_addr = found_zero - (found_zero %
> host_ratio);
> + /*
> + * This host page has gone, the next loop iteration
> starts
> + * from the next page with a 1 bit
> + */
> + search_start = discard_start_addr + host_ratio;
> + } else {
> + /*
> + * No discards on this iteration, next loop starts from
> + * next 1 bit
> + */
> + search_start = found_zero + 1;
change for this
found_set = found_zero + 1;
> + }
> + }
> + /* Find the next 1 for the next iteration */
> + found_set = find_next_bit(ms->sentmap, last + 1, search_start);
and move previous line to:
> + if (do_discard) {
> + unsigned long page;
> +
> + /* Tell the destination to discard this page */
> + postcopy_discard_send_range(ms, pds, discard_start_addr,
> + discard_start_addr + host_ratio - 1);
> + /* Clean up the bitmap */
> + for (page = discard_start_addr;
> + page < discard_start_addr + host_ratio; page++) {
> + /* All pages in this host page are now not sent */
> + clear_bit(page, ms->sentmap);
> +
> + /*
> + * Remark them as dirty, updating the count for any pages
> + * that weren't previously dirty.
> + */
> + migration_dirty_pages += !test_and_set_bit(page,
> +
> migration_bitmap);
> + }
to here
/* Find the next 1 for the next iteration */
found_set = find_next_bit(ms->sentmap, last + 1,
search_start);
}
> + }
?
> +
> + /*
> + * Second pass: Ensure that all partially dirty host pages are made
> + * fully dirty.
> + */
> + found_set = find_next_bit(migration_bitmap, last + 1, first);
> + while (found_set <= last) {
> + bool do_dirty = false;
> + unsigned long dirty_start_addr;
> + /*
> + * If the start of this run of pages is in the middle of a host
> + * page, then we need to mark the whole of this host page dirty
> + */
> + if (found_set % host_ratio) {
> + do_dirty = true;
> + found_set -= found_set % host_ratio;
> + dirty_start_addr = found_set;
> + search_start = found_set + host_ratio;
> + } else {
> + /* Find the end of this run */
> + unsigned long found_zero;
> + found_zero = find_next_zero_bit(migration_bitmap, last + 1,
> + found_set + 1);
> + /*
> + * If the 0 isn't at the start of a host page, then the
> + * run of 1's doesn't finish at the end of a host page
> + * and we need to discard.
> + */
> + if (found_zero % host_ratio) {
> + do_dirty = true;
> + dirty_start_addr = found_zero - (found_zero %
> host_ratio);
> + /*
> + * This host page has gone, the next loop iteration
> starts
> + * from the next page with a 1 bit
> + */
> + search_start = dirty_start_addr + host_ratio;
> + } else {
> + /*
> + * No discards on this iteration, next loop starts from
> + * next 1 bit
> + */
> + search_start = found_zero + 1;
> + }
> + }
> +
> + /* Find the next 1 for the next iteration */
> + found_set = find_next_bit(migration_bitmap, last + 1,
> search_start);
> +
> + if (do_dirty) {
> + unsigned long page;
> +
> + if (test_bit(dirty_start_addr, ms->sentmap)) {
> + /*
> + * If the page being redirtied is marked as sent, then it
> + * must have been fully sent (otherwise it would have
> been
> + * discarded by the previous pass.)
> + * Discard it now.
> + */
> + postcopy_discard_send_range(ms, pds, dirty_start_addr,
> + dirty_start_addr +
> + host_ratio - 1);
> + }
> +
> + /* Clean up the bitmap */
> + for (page = dirty_start_addr;
> + page < dirty_start_addr + host_ratio; page++) {
> +
> + /* Clear the sentmap bits for the discard case above */
> + clear_bit(page, ms->sentmap);
> +
> + /*
> + * Mark them as dirty, updating the count for any pages
> + * that weren't previously dirty.
> + */
> + migration_dirty_pages += !test_and_set_bit(page,
> +
> migration_bitmap);
> + }
> + }
> + }
This is exactly the same code than the previous half of the function,
you just need to factor out in a function?
walk_btimap_host_page_chunks or whatever, and pass the two bits that
change? the bitmap, and what to do with the ranges that are not there?
