Commit 8324ef86 authored by Wei Yang's avatar Wei Yang Committed by Dr. David Alan Gilbert
Browse files

migration/postcopy: not necessary to do discard when canonicalizing bitmap 



All pages, either partially sent or partially dirty, will be discarded in
postcopy_send_discard_bm_ram(), since we update the unsentmap to be
unsentmap = unsentmap | dirty in ram_postcopy_send_discard_bitmap().

This is not necessary to do discard when canonicalizing bitmap. And by
doing so, we separate the page discard into two individual steps:

  * canonicalize bitmap
  * discard page

Signed-off-by: default avatarWei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190819061843.28642-2-richardw.yang@linux.intel.com>
Reviewed-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: default avatarDr. David Alan Gilbert <dgilbert@redhat.com>
parent 91490583

migration/ram.c

+1 −13
Original line number Diff line number Diff line
@@ -2928,7 +2928,7 @@ static int postcopy_each_ram_send_discard(MigrationState *ms) 
}



/**

 * postcopy_chunk_hostpages_pass: canocalize bitmap in hostpages

 * postcopy_chunk_hostpages_pass: canonicalize bitmap in hostpages

 *

 * Helper for postcopy_chunk_hostpages; it's called twice to

 * canonicalize the two bitmaps, that are similar, but one is
@@ -2991,18 +2991,6 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass, 
                                                             host_ratio);

            run_start = QEMU_ALIGN_UP(run_start, host_ratio);



            /* Tell the destination to discard this page */

            if (unsent_pass || !test_bit(fixup_start_addr, unsentmap)) {

                /* For the unsent_pass we:

                 *     discard partially sent pages

                 * For the !unsent_pass (dirty) we:

                 *     discard partially dirty pages that were sent

                 *     (any partially sent pages were already discarded

                 *     by the previous unsent_pass)

                 */

                postcopy_discard_send_range(ms, fixup_start_addr, host_ratio);

            }



            /* Clean up the bitmap */

            for (page = fixup_start_addr;

                 page < fixup_start_addr + host_ratio; page++) {