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migration/postcopy: unsentmap is not necessary for postcopy
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Commit f3f491f ('Postcopy: Maintain unsentmap') introduced
unsentmap to track not yet sent pages.

This is not necessary since:

    * unsentmap is a sub-set of bmap before postcopy start
    * unsentmap is the summation of bmap and unsentmap after canonicalizing

This patch just removes it.

Signed-off-by: Wei Yang <richardw.yang@linux.intel.com>
Message-Id: <20190819061843.28642-3-richardw.yang@linux.intel.com>
Reviewed-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
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@dagrh
Wei Yang authored and dagrh committed Sep 25, 2019
1 parent 8324ef8 commit 1e7cf8c
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Showing 2 changed files with 14 additions and 72 deletions.
6 changes: 0 additions & 6 deletions include/exec/ram_addr.h
View file
Expand Up @@ -44,12 +44,6 @@ struct RAMBlock {
size_t page_size;
/* dirty bitmap used during migration */
unsigned long *bmap;
/* bitmap of pages that haven't been sent even once
* only maintained and used in postcopy at the moment
* where it's used to send the dirtymap at the start
* of the postcopy phase
*/
unsigned long *unsentmap;
/* bitmap of already received pages in postcopy */
unsigned long *receivedmap;

Expand Down
80 changes: 14 additions & 66 deletions migration/ram.c
View file
Expand Up @@ -2348,7 +2348,7 @@ static bool get_queued_page(RAMState *rs, PageSearchStatus *pss)
dirty = test_bit(page, block->bmap);
if (!dirty) {
trace_get_queued_page_not_dirty(block->idstr, (uint64_t)offset,
page, test_bit(page, block->unsentmap));
page, test_bit(page, block->bmap));
} else {
trace_get_queued_page(block->idstr, (uint64_t)offset, page);
}
Expand Down Expand Up @@ -2619,10 +2619,6 @@ static int ram_save_host_page(RAMState *rs, PageSearchStatus *pss,
}

pages += tmppages;
if (pss->block->unsentmap) {
clear_bit(pss->page, pss->block->unsentmap);
}

pss->page++;
} while ((pss->page & (pagesize_bits - 1)) &&
offset_in_ramblock(pss->block, pss->page << TARGET_PAGE_BITS));
Expand Down Expand Up @@ -2776,8 +2772,6 @@ static void ram_save_cleanup(void *opaque)
block->clear_bmap = NULL;
g_free(block->bmap);
block->bmap = NULL;
g_free(block->unsentmap);
block->unsentmap = NULL;
}

xbzrle_cleanup();
Expand Down Expand Up @@ -2857,8 +2851,6 @@ void ram_postcopy_migrated_memory_release(MigrationState *ms)
* Returns zero on success
*
* Callback from postcopy_each_ram_send_discard for each RAMBlock
* Note: At this point the 'unsentmap' is the processed bitmap combined
* with the dirtymap; so a '1' means it's either dirty or unsent.
*
* @ms: current migration state
* @block: RAMBlock to discard
Expand All @@ -2867,17 +2859,17 @@ static int postcopy_send_discard_bm_ram(MigrationState *ms, RAMBlock *block)
{
unsigned long end = block->used_length >> TARGET_PAGE_BITS;
unsigned long current;
unsigned long *unsentmap = block->unsentmap;
unsigned long *bitmap = block->bmap;

for (current = 0; current < end; ) {
unsigned long one = find_next_bit(unsentmap, end, current);
unsigned long one = find_next_bit(bitmap, end, current);
unsigned long zero, discard_length;

if (one >= end) {
break;
}

zero = find_next_zero_bit(unsentmap, end, one + 1);
zero = find_next_zero_bit(bitmap, end, one + 1);

if (zero >= end) {
discard_length = end - one;
Expand Down Expand Up @@ -2938,16 +2930,12 @@ static int postcopy_each_ram_send_discard(MigrationState *ms)
* clean, not a mix. This function canonicalizes the bitmaps.
*
* @ms: current migration state
* @unsent_pass: if true we need to canonicalize partially unsent host pages
* otherwise we need to canonicalize partially dirty host pages
* @block: block that contains the page we want to canonicalize
*/
static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
RAMBlock *block)
static void postcopy_chunk_hostpages_pass(MigrationState *ms, RAMBlock *block)
{
RAMState *rs = ram_state;
unsigned long *bitmap = block->bmap;
unsigned long *unsentmap = block->unsentmap;
unsigned int host_ratio = block->page_size / TARGET_PAGE_SIZE;
unsigned long pages = block->used_length >> TARGET_PAGE_BITS;
unsigned long run_start;
Expand All @@ -2957,13 +2945,8 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
return;
}

if (unsent_pass) {
/* Find a sent page */
run_start = find_next_zero_bit(unsentmap, pages, 0);
} else {
/* Find a dirty page */
run_start = find_next_bit(bitmap, pages, 0);
}
/* Find a dirty page */
run_start = find_next_bit(bitmap, pages, 0);

while (run_start < pages) {

Expand All @@ -2973,11 +2956,7 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
*/
if (QEMU_IS_ALIGNED(run_start, host_ratio)) {
/* Find the end of this run */
if (unsent_pass) {
run_start = find_next_bit(unsentmap, pages, run_start + 1);
} else {
run_start = find_next_zero_bit(bitmap, pages, run_start + 1);
}
run_start = find_next_zero_bit(bitmap, pages, 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
Expand All @@ -2994,9 +2973,6 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
/* 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.
Expand All @@ -3005,13 +2981,8 @@ static void postcopy_chunk_hostpages_pass(MigrationState *ms, bool unsent_pass,
}
}

if (unsent_pass) {
/* Find the next sent page for the next iteration */
run_start = find_next_zero_bit(unsentmap, pages, run_start);
} else {
/* Find the next dirty page for the next iteration */
run_start = find_next_bit(bitmap, pages, run_start);
}
/* Find the next dirty page for the next iteration */
run_start = find_next_bit(bitmap, pages, run_start);
}
}

Expand All @@ -3033,13 +3004,10 @@ static int postcopy_chunk_hostpages(MigrationState *ms, RAMBlock *block)
{
postcopy_discard_send_init(ms, block->idstr);

/* First pass: Discard all partially sent host pages */
postcopy_chunk_hostpages_pass(ms, true, block);
/*
* Second pass: Ensure that all partially dirty host pages are made
* fully dirty.
* Ensure that all partially dirty host pages are made fully dirty.
*/
postcopy_chunk_hostpages_pass(ms, false, block);
postcopy_chunk_hostpages_pass(ms, block);

postcopy_discard_send_finish(ms);
return 0;
Expand Down Expand Up @@ -3077,32 +3045,16 @@ int ram_postcopy_send_discard_bitmap(MigrationState *ms)
rs->last_page = 0;

RAMBLOCK_FOREACH_NOT_IGNORED(block) {
unsigned long pages = block->used_length >> TARGET_PAGE_BITS;
unsigned long *bitmap = block->bmap;
unsigned long *unsentmap = block->unsentmap;

if (!unsentmap) {
/* We don't have a safe way to resize the sentmap, so
* if the bitmap was resized it will be NULL at this
* point.
*/
error_report("migration ram resized during precopy phase");
rcu_read_unlock();
return -EINVAL;
}
/* Deal with TPS != HPS and huge pages */
ret = postcopy_chunk_hostpages(ms, block);
if (ret) {
rcu_read_unlock();
return ret;
}

/*
* Update the unsentmap to be unsentmap = unsentmap | dirty
*/
bitmap_or(unsentmap, unsentmap, bitmap, pages);
#ifdef DEBUG_POSTCOPY
ram_debug_dump_bitmap(unsentmap, true, pages);
ram_debug_dump_bitmap(block->bmap, true,
block->used_length >> TARGET_PAGE_BITS);
#endif
}
trace_ram_postcopy_send_discard_bitmap();
Expand Down Expand Up @@ -3270,10 +3222,6 @@ static void ram_list_init_bitmaps(void)
bitmap_set(block->bmap, 0, pages);
block->clear_bmap_shift = shift;
block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift));
if (migrate_postcopy_ram()) {
block->unsentmap = bitmap_new(pages);
bitmap_set(block->unsentmap, 0, pages);
}
}
}
}
Expand Down

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