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Host page!=target page: Cleanup bitmaps

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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 <dgilbert@redhat.com>
Reviewed-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-11-05 18:11:15 +00:00 committed by Juan Quintela
parent 35ecd943e7
commit 99e314ebca
1 changed files with 172 additions and 0 deletions
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172
migration/ram.c
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@ -1583,6 +1583,171 @@ static int postcopy_each_ram_send_discard(MigrationState *ms)
return 0;
}
/*
* Helper for postcopy_chunk_hostpages; it's called twice to cleanup
* the two bitmaps, that are similar, but one is inverted.
*
* We search for runs of target-pages that don't start or end on a
* host page boundary;
* unsent_pass=true: Cleans up partially unsent host pages by searching
* the unsentmap
* unsent_pass=false: Cleans up partially dirty host pages by searching
* the main migration bitmap
*
*/
static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
RAMBlock *block,
PostcopyDiscardState *pds)
{
unsigned long *bitmap;
unsigned long *unsentmap;
unsigned int host_ratio = qemu_host_page_size / TARGET_PAGE_SIZE;
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 run_start;
bitmap = atomic_rcu_read(&migration_bitmap_rcu)->bmap;
unsentmap = atomic_rcu_read(&migration_bitmap_rcu)->unsentmap;
if (unsent_pass) {
/* Find a sent page */
run_start = find_next_zero_bit(unsentmap, last + 1, first);
} else {
/* Find a dirty page */
run_start = find_next_bit(bitmap, last + 1, first);
}
while (run_start <= last) {
bool do_fixup = false;
unsigned long fixup_start_addr;
unsigned long host_offset;
/*
* If the start of this run of pages is in the middle of a host
* page, then we need to fixup this host page.
*/
host_offset = run_start % host_ratio;
if (host_offset) {
do_fixup = true;
run_start -= host_offset;
fixup_start_addr = run_start;
/* For the next pass */
run_start = run_start + host_ratio;
} else {
/* Find the end of this run */
unsigned long run_end;
if (unsent_pass) {
run_end = find_next_bit(unsentmap, last + 1, run_start + 1);
} else {
run_end = find_next_zero_bit(bitmap, last + 1, run_start + 1);
}
/*
* If the end isn't at the start of a host page, then the
* run doesn't finish at the end of a host page
* and we need to discard.
*/
host_offset = run_end % host_ratio;
if (host_offset) {
do_fixup = true;
fixup_start_addr = run_end - host_offset;
/*
* This host page has gone, the next loop iteration starts
* from after the fixup
*/
run_start = fixup_start_addr + host_ratio;
} else {
/*
* No discards on this iteration, next loop starts from
* next sent/dirty page
*/
run_start = run_end + 1;
}
}
if (do_fixup) {
unsigned long page;
/* 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, pds, fixup_start_addr,
host_ratio);
}
/* Clean up the bitmap */
for (page = fixup_start_addr;
page < fixup_start_addr + host_ratio; page++) {
/* All pages in this host page are now not sent */
set_bit(page, unsentmap);
/*
* Remark them as dirty, updating the count for any pages
* that weren't previously dirty.
*/
migration_dirty_pages += !test_and_set_bit(page, bitmap);
}
}
if (unsent_pass) {
/* Find the next sent page for the next iteration */
run_start = find_next_zero_bit(unsentmap, last + 1,
run_start);
} else {
/* Find the next dirty page for the next iteration */
run_start = find_next_bit(bitmap, last + 1, run_start);
}
}
}
/*
* Utility for the outgoing postcopy code.
*
* Discard any partially sent host-page size chunks, mark any partially
* dirty host-page size chunks as all dirty.
*
* Returns: 0 on success
*/
static int postcopy_chunk_hostpages(MigrationState *ms)
{
struct RAMBlock *block;
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;
QLIST_FOREACH_RCU(block, &ram_list.blocks, next) {
unsigned long first = block->offset >> TARGET_PAGE_BITS;
PostcopyDiscardState *pds =
postcopy_discard_send_init(ms, first, block->idstr);
/* First pass: Discard all partially sent host pages */
postcopy_chunk_hostpages_pass(ms, true, block, pds);
/*
* Second pass: Ensure that all partially dirty host pages are made
* fully dirty.
*/
postcopy_chunk_hostpages_pass(ms, false, block, pds);
postcopy_discard_send_finish(ms, pds);
} /* ram_list loop */
return 0;
}
/*
* Transmit the set of pages to be discarded after precopy to the target
* these are pages that:
@ -1613,6 +1778,13 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
return -EINVAL;
}
/* Deal with TPS != HPS */
ret = postcopy_chunk_hostpages(ms);
if (ret) {
rcu_read_unlock();
return ret;
}
/*
* Update the unsentmap to be unsentmap = unsentmap | dirty
*/