From: Nikolay Borisov <nbori...@suse.com> Implement the outgoing migration side for the 'fixed-ram' capability.
A bitmap is introduced to track which pages have been written in the migration file. Pages are written at a fixed location for every ramblock. Zero pages are ignored as they'd be zero in the destination migration as well. The migration stream is altered to put the dirty pages for a ramblock after its header instead of having a sequential stream of pages that follow the ramblock headers. Since all pages have a fixed location, RAM_SAVE_FLAG_EOS is no longer generated on every migration iteration. Without fixed-ram (current): ramblock 1 header|ramblock 2 header|...|RAM_SAVE_FLAG_EOS|stream of pages (iter 1)|RAM_SAVE_FLAG_EOS|stream of pages (iter 2)|... With fixed-ram (new): ramblock 1 header|ramblock 1 fixed-ram header|ramblock 1 pages (fixed offsets)|ramblock 2 header|ramblock 2 fixed-ram header|ramblock 2 pages (fixed offsets)|...|RAM_SAVE_FLAG_EOS where: - ramblock header: the generic information for a ramblock, such as idstr, used_len, etc. - ramblock fixed-ram header: the new information added by this feature: bitmap of pages written, bitmap size and offset of pages in the migration file. Signed-off-by: Nikolay Borisov <nbori...@suse.com> Signed-off-by: Fabiano Rosas <faro...@suse.de> --- include/exec/ramblock.h | 8 ++++ migration/options.c | 3 -- migration/ram.c | 98 ++++++++++++++++++++++++++++++++++++----- 3 files changed, 96 insertions(+), 13 deletions(-) diff --git a/include/exec/ramblock.h b/include/exec/ramblock.h index 69c6a53902..e0e3f16852 100644 --- a/include/exec/ramblock.h +++ b/include/exec/ramblock.h @@ -44,6 +44,14 @@ struct RAMBlock { size_t page_size; /* dirty bitmap used during migration */ unsigned long *bmap; + /* shadow dirty bitmap used when migrating to a file */ + unsigned long *shadow_bmap; + /* + * offset in the file pages belonging to this ramblock are saved, + * used only during migration to a file. + */ + off_t bitmap_offset; + uint64_t pages_offset; /* bitmap of already received pages in postcopy */ unsigned long *receivedmap; diff --git a/migration/options.c b/migration/options.c index 2622d8c483..9f693d909f 100644 --- a/migration/options.c +++ b/migration/options.c @@ -271,12 +271,9 @@ bool migrate_events(void) bool migrate_fixed_ram(void) { -/* MigrationState *s = migrate_get_current(); return s->capabilities[MIGRATION_CAPABILITY_FIXED_RAM]; -*/ - return false; } bool migrate_ignore_shared(void) diff --git a/migration/ram.c b/migration/ram.c index 92769902bb..152a03604f 100644 --- a/migration/ram.c +++ b/migration/ram.c @@ -1157,12 +1157,18 @@ static int save_zero_page(RAMState *rs, PageSearchStatus *pss, return 0; } + stat64_add(&mig_stats.zero_pages, 1); + + if (migrate_fixed_ram()) { + /* zero pages are not transferred with fixed-ram */ + clear_bit(offset >> TARGET_PAGE_BITS, pss->block->shadow_bmap); + return 1; + } + len += save_page_header(pss, file, pss->block, offset | RAM_SAVE_FLAG_ZERO); qemu_put_byte(file, 0); len += 1; ram_release_page(pss->block->idstr, offset); - - stat64_add(&mig_stats.zero_pages, 1); ram_transferred_add(len); /* @@ -1220,14 +1226,20 @@ static int save_normal_page(PageSearchStatus *pss, RAMBlock *block, { QEMUFile *file = pss->pss_channel; - ram_transferred_add(save_page_header(pss, pss->pss_channel, block, - offset | RAM_SAVE_FLAG_PAGE)); - if (async) { - qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE, - migrate_release_ram() && - migration_in_postcopy()); + if (migrate_fixed_ram()) { + qemu_put_buffer_at(file, buf, TARGET_PAGE_SIZE, + block->pages_offset + offset); + set_bit(offset >> TARGET_PAGE_BITS, block->shadow_bmap); } else { - qemu_put_buffer(file, buf, TARGET_PAGE_SIZE); + ram_transferred_add(save_page_header(pss, pss->pss_channel, block, + offset | RAM_SAVE_FLAG_PAGE)); + if (async) { + qemu_put_buffer_async(file, buf, TARGET_PAGE_SIZE, + migrate_release_ram() && + migration_in_postcopy()); + } else { + qemu_put_buffer(file, buf, TARGET_PAGE_SIZE); + } } ram_transferred_add(TARGET_PAGE_SIZE); stat64_add(&mig_stats.normal_pages, 1); @@ -2475,6 +2487,8 @@ static void ram_save_cleanup(void *opaque) block->clear_bmap = NULL; g_free(block->bmap); block->bmap = NULL; + g_free(block->shadow_bmap); + block->shadow_bmap = NULL; } xbzrle_cleanup(); @@ -2842,6 +2856,7 @@ static void ram_list_init_bitmaps(void) */ block->bmap = bitmap_new(pages); bitmap_set(block->bmap, 0, pages); + block->shadow_bmap = bitmap_new(block->used_length >> TARGET_PAGE_BITS); block->clear_bmap_shift = shift; block->clear_bmap = bitmap_new(clear_bmap_size(pages, shift)); } @@ -2979,6 +2994,44 @@ void qemu_guest_free_page_hint(void *addr, size_t len) } } +#define FIXED_RAM_HDR_VERSION 1 +struct FixedRamHeader { + uint32_t version; + uint64_t page_size; + uint64_t bitmap_offset; + uint64_t pages_offset; + /* end of v1 */ +} QEMU_PACKED; + +static void fixed_ram_insert_header(QEMUFile *file, RAMBlock *block) +{ + g_autofree struct FixedRamHeader *header; + size_t header_size, bitmap_size; + long num_pages; + + header = g_new0(struct FixedRamHeader, 1); + header_size = sizeof(struct FixedRamHeader); + + num_pages = block->used_length >> TARGET_PAGE_BITS; + bitmap_size = BITS_TO_LONGS(num_pages) * sizeof(unsigned long); + + /* + * Save the file offsets of where the bitmap and the pages should + * go as they are written at the end of migration and during the + * iterative phase, respectively. + */ + block->bitmap_offset = qemu_get_offset(file) + header_size; + block->pages_offset = ROUND_UP(block->bitmap_offset + + bitmap_size, 0x100000); + + header->version = cpu_to_be32(FIXED_RAM_HDR_VERSION); + header->page_size = cpu_to_be64(TARGET_PAGE_SIZE); + header->bitmap_offset = cpu_to_be64(block->bitmap_offset); + header->pages_offset = cpu_to_be64(block->pages_offset); + + qemu_put_buffer(file, (uint8_t *) header, header_size); +} + /* * Each of ram_save_setup, ram_save_iterate and ram_save_complete has * long-running RCU critical section. When rcu-reclaims in the code @@ -3028,6 +3081,12 @@ static int ram_save_setup(QEMUFile *f, void *opaque) if (migrate_ignore_shared()) { qemu_put_be64(f, block->mr->addr); } + + if (migrate_fixed_ram()) { + fixed_ram_insert_header(f, block); + /* prepare offset for next ramblock */ + qemu_set_offset(f, block->pages_offset + block->used_length, SEEK_SET); + } } } @@ -3061,6 +3120,20 @@ static int ram_save_setup(QEMUFile *f, void *opaque) return 0; } +static void ram_save_shadow_bmap(QEMUFile *f) +{ + RAMBlock *block; + + RAMBLOCK_FOREACH_MIGRATABLE(block) { + long num_pages = block->used_length >> TARGET_PAGE_BITS; + long bitmap_size = BITS_TO_LONGS(num_pages) * sizeof(unsigned long); + qemu_put_buffer_at(f, (uint8_t *)block->shadow_bmap, bitmap_size, + block->bitmap_offset); + /* to catch any thread late sending pages */ + block->shadow_bmap = NULL; + } +} + /** * ram_save_iterate: iterative stage for migration * @@ -3179,7 +3252,6 @@ out: qemu_put_be64(f, RAM_SAVE_FLAG_EOS); qemu_fflush(f); ram_transferred_add(8); - ret = qemu_file_get_error(f); } if (ret < 0) { @@ -3256,7 +3328,13 @@ static int ram_save_complete(QEMUFile *f, void *opaque) if (migrate_multifd() && !migrate_multifd_flush_after_each_section()) { qemu_put_be64(f, RAM_SAVE_FLAG_MULTIFD_FLUSH); } + + if (migrate_fixed_ram()) { + ram_save_shadow_bmap(f); + } + qemu_put_be64(f, RAM_SAVE_FLAG_EOS); + qemu_fflush(f); return 0; -- 2.35.3