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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: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190819061843.28642-2-richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
This commit is contained in:
Wei Yang 2019-08-19 14:18:41 +08:00 committed by Dr. David Alan Gilbert
parent 91490583f3
commit 8324ef86f0
1 changed files with 1 additions and 13 deletions
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14
migration/ram.c
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@ -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++) {