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ram_find_and_save_block: Split out the finding

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Split out the finding of the dirty page and all the wrap detection
into a separate function since it was getting a bit hairy.

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Message-Id: <1443018431-11170-3-git-send-email-dgilbert@redhat.com>
Reviewed-by: Amit Shah <amit.shah@redhat.com>

[Fix comment -- Amit]
Signed-off-by: Amit Shah <amit.shah@redhat.com>
This commit is contained in:
Dr. David Alan Gilbert 2015-09-23 15:27:11 +01:00 committed by Amit Shah
parent b8fb8cb748
commit b9e6092814
1 changed files with 59 additions and 25 deletions
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84
migration/ram.c
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@ -917,6 +917,59 @@ static int ram_save_compressed_page(QEMUFile *f, RAMBlock *block,
return pages;
}
/*
* Find the next dirty page and update any state associated with
* the search process.
*
* Returns: True if a page is found
*
* @f: Current migration stream.
* @pss: Data about the state of the current dirty page scan.
* @*again: Set to false if the search has scanned the whole of RAM
*/
static bool find_dirty_block(QEMUFile *f, PageSearchStatus *pss,
bool *again)
{
pss->offset = migration_bitmap_find_and_reset_dirty(pss->block,
pss->offset);
if (pss->complete_round && pss->block == last_seen_block &&
pss->offset >= last_offset) {
/*
* We've been once around the RAM and haven't found anything.
* Give up.
*/
*again = false;
return false;
}
if (pss->offset >= pss->block->used_length) {
/* Didn't find anything in this RAM Block */
pss->offset = 0;
pss->block = QLIST_NEXT_RCU(pss->block, next);
if (!pss->block) {
/* Hit the end of the list */
pss->block = QLIST_FIRST_RCU(&ram_list.blocks);
/* Flag that we've looped */
pss->complete_round = true;
ram_bulk_stage = false;
if (migrate_use_xbzrle()) {
/* If xbzrle is on, stop using the data compression at this
* point. In theory, xbzrle can do better than compression.
*/
flush_compressed_data(f);
compression_switch = false;
}
}
/* Didn't find anything this time, but try again on the new block */
*again = true;
return false;
} else {
/* Can go around again, but... */
*again = true;
/* We've found something so probably don't need to */
return true;
}
}
/**
* ram_find_and_save_block: Finds a dirty page and sends it to f
*
@ -935,6 +988,7 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
{
PageSearchStatus pss;
int pages = 0;
bool again, found;
pss.block = last_seen_block;
pss.offset = last_offset;
@ -944,29 +998,10 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
pss.block = QLIST_FIRST_RCU(&ram_list.blocks);
}
while (true) {
pss.offset = migration_bitmap_find_and_reset_dirty(pss.block,
pss.offset);
if (pss.complete_round && pss.block == last_seen_block &&
pss.offset >= last_offset) {
break;
}
if (pss.offset >= pss.block->used_length) {
pss.offset = 0;
pss.block = QLIST_NEXT_RCU(pss.block, next);
if (!pss.block) {
pss.block = QLIST_FIRST_RCU(&ram_list.blocks);
pss.complete_round = true;
ram_bulk_stage = false;
if (migrate_use_xbzrle()) {
/* If xbzrle is on, stop using the data compression at this
* point. In theory, xbzrle can do better than compression.
*/
flush_compressed_data(f);
compression_switch = false;
}
}
} else {
do {
found = find_dirty_block(f, &pss, &again);
if (found) {
if (compression_switch && migrate_use_compression()) {
pages = ram_save_compressed_page(f, pss.block, pss.offset,
last_stage,
@ -979,10 +1014,9 @@ static int ram_find_and_save_block(QEMUFile *f, bool last_stage,
/* if page is unmodified, continue to the next */
if (pages > 0) {
last_sent_block = pss.block;
break;
}
}
}
} while (!pages && again);
last_seen_block = pss.block;
last_offset = pss.offset;